Home

News

Forums

Hardware

CPUs

Mainboards

Video

Guides

CPU Prices

Memory Prices

Shop



Sharky Extreme :


Latest News


- Outdoor Life: Panasonic Puts 3G Wireless Into Rugged Notebooks
- Averatec Launches Lightweight Turion 64 X2 Laptop
- Acer Fires Up Two New Ferrari Notebooks
- Belkin Debuts Docking Station for ExpressCard-Equipped Notebooks
- Logitech 5.1 Speaker System Puts Your Ears At Eye Level
News Archives

Features

- SharkyExtreme.com: Interview with ATI's Terry Makedon
- SharkyExtreme.com: Interview with Seagate's Joni Clark
- Half-Life 2 Review
- DOOM 3 Review
- Unreal Tournament 2004 Review

Buyer's Guides

- September High-end Gaming PC Buyer's Guide
- September Value Gaming PC Buyer's Guide
- October Extreme Gaming PC Buyer's Guide

HARDWARE

  • CPUs


  • Motherboards

    - Gigabyte GA-965P-DS3 Motherboard Review
    - DFI LANPARTY UT nF4 Ultra-D Motherboard Review

  • Video Cards

    - Gigabyte GeForce 7600 GT 256MB Review
    - ASUS EN7900GT TOP 256MB Review
    - ASUS EN7600GT Silent 256MB Review
    - Biostar GeForce 7900 GT 256MB Review





  • SharkyForums.Com - Print: What would you think about putting RDRAM on a Video Card

    What would you think about putting RDRAM on a Video Card
    By Arcadian January 06, 2001, 03:30 PM

    I wanted to start a technical discussion today, and see what people would think about putting RDRAM on a video card instead of SDRAM.

    One of the buggest bottlenecks in video cards, even on the GeForce 2 Ultra, is memory bandwidth. Many people believe that more memory bandwidth will allow for better frame rates, and faster graphics for very intense games.

    Correct me if I'm wrong, but I believe that the current limit for memory bandwidth on a modern video card is using 220MHz memory with DDR technology, thus allowing for the equivalent of 440MHz video DDR memory.

    What if instead of DDR SDRAM, video card manufacturers use RDRAM. First, let's talk about memory speed. It is known that direct connect memory can reach much higher speeds than system memory, which have several loads connected together. While system DDR memory maxes out at 133MHz (PC2100), video DDR memory can go up to 200MHz (440MHz DDR, again correct me if I'm wrong).

    If we used Rambus memory, which easily reaches 400MHz in a system (PC800 RDRAM), the direct connect version should reach up to 500MHz or 600MHz (1GHz or 1.2GHz DDR, since Rambus also uses double data rate technology, in case you didn't know). However, we'll be conservative, and assume an effective 1GHz for video Rambus.

    Now, let's consider the pin count. Rambus is 16-bit wide, and SDRAM is 64-bit wide. Most video cards make a dual channel SDRAM interface of 128 bits. So, for the same amount of pins of a DDR interface, you can create a connection of 8 Rambus channels. This will effectively quadruple the bandwidth of a standard dual channel connection.

    So let's do a simple calculation. Let's say that current DDR video memory interfaces get 440MHz, effective speed, 64 bits (or 8 bytes per clock), and 2 channels. The bandwidth would then be 440 * 8 * 2 = 7.04GB/s. Let's take the same calculation for a Rambus interface. From before, we can assume we get at least 1GHz per channel for speed, 16 bits (or 2 bytes per clock), and 8 channels. The bandwidth would then be 1000 * 2 * 8, or 16GB/s. That's more than twice the bandwidth for a similar connection! We were also being fairly conservative about the speeds of a direct Rambus connection. I believe I read somewhere that they were about to come out with a 1.6GHz direct Rambus connection, but I don't know whether that ever materialized. If that were to come out some time in the future, though, we could talk about 1600 * 2 * 8 = 25.6GB/s video memory bandwidth!!!

    Now there are two things about Rambus system memory that are disconcerning to the rest of us. The first is latency, and the second is price.

    For the first, latency, we know that Rambus does have higher latencies than DDR SDRAM, mostly because of the packet decoding process that has to go on, since Rambus data is packet based. However, it is known that a lot of Rambus latency comes from the system memory design scheme that allows for multiple loads. Direct Rambus interfaces are faster than Rambus in a PC system. Therefore, latency should not have an adverse affect performance over a similar DDR interface.

    Second, price, is also a consern. However, it is known that the largest expense for Rambus memory is the RIMM module. In a direct connection, Rambus is actually cheaper than SDRAM. However, prices will be affected by lower volumes, since a new technology of direct video Rambus would be expensive. But then again, Driect DDR interfaces are also relatively low volume, so I am thinking that a video Rambus would not be much more expensive than video DDR.

    So there you have it. Obviously if everything else is equal, then Rambus should be the best things to ever happen to the video world. But, things may not be so equal, and I was hoping to get a few people's opinions on how this kind of setup would work. Do you think that using Rambus in video cards would be worth it? As we have seen, bandwidths can easily be doubled, or even tripled over current technologies. How would you like frame rates of 120+ fps at 1600*1200*32 with all features turned on in your favorite games?

    Please reply, and have fun with this. I am hoping for technical responses, but feel free to toss in an opinion or two, as well. Later .

    By Assmonkey January 06, 2001, 03:39 PM

    First off, i think you talk to much.
    second off, Yes RDRAM i think would be sweet, its just to expensive right now.

    By Arcadian January 06, 2001, 04:26 PM

    quote:Originally posted by Assmonkey:
    First off, i think you talk to much.
    second off, Yes RDRAM i think would be sweet, its just to expensive right now.

    Wow. This is even more of an insightful technical response than I could ever have hoped for....

    Maybe I've been mislead to think that the highly technical forum might yield some interesting discussion in some rarely explored areas of interest. Maybe I should go back to the CPU forums and ask how to get another 20MHz out of an already highly overclocked 700MHz Duron. Or, maybe assmonkeys are just too stupid to know anything about highly technical subjects such as high bandwidth memory technologies, and they should learn when to keep their mouths shut and not insult someone who is simply trying to entice some technical discussions. Perhaps you should move on to the next mindless overclocking topic and kindly keep future arrogant responses to yourself.

    [edit] As an afterthought, I just want to say that I really don't mean to come down so hard on the assmonkey, but it really does upset me when the only response I get to a writeup that I spent almost a half hour on, was that I talk too much. I know that I did invite comments and opinions, but I still did not appreciate the insult.

    By blk-sabbath-fan January 06, 2001, 04:33 PM

    [Original message edited out]

    We won't tolerate personal attacks, blk-sabbath-fan - this is a perfectly valid discussion, and I, like Arcadian would like to see intelligent conversation to the possibility of RDRAM on video cards, thank you.

    Ciao!

    By Arcadian January 06, 2001, 04:57 PM

    You've got me figured all wrong, man. I am not picking on the assmonkey because his response was short, but because his response was insulting and innapropriate. And you're not helping things with yours.

    I have a lot of posts, because I've been a member here since this forum first began. I have a life except for times when I'm bored, and during those times, I look for some interesting discussions on this board.

    In case you haven't noticed, we are in the Highly Technical Forum. I spent a good amount of time thinking up and writing about a topic that not many people have talked about so far. If you think this is dorky, then you shouldn't be here.

    Many people that come to this site either look to get help, or help others. I happen to participate in the latter quite a bit, and give knowledge to many readers that want to know more about computer architecture. Again, if you are not interested in topics of computer architecture, then you should be surfing around some Black Sabbath fan sites, and downloading concert times, or whatever floats your boat.

    However, there are quite a few people that are interested in highly technical discussions, and for those people, both you and the assmonkey are wasting space with your bullsh!t. I hope you can be respectful, and keep this forum close to what it is intended to be. If not, I'm sure the moderators here would have no problem barring you from the boards.

    I have no problem with opinions that Rambus is expensive, or that you may not think it is a valid idea. Backing up your claims would be very appropriate, but it isn't necessary. However, I think you are crossing the line when you make comments such as yours or the assmonkey's. Please make sure that you treat others on this board with respect, and you will be treated accordingly. Have a nice day.

    By i954 January 06, 2001, 05:19 PM

    I don't enjoy flame wars. Take it easy people. Maybe the "you talk too much" remark was made as a joke, but "Wow. This is even more of an insightful technical response than I could ever have hoped for.... " is kind of insulting in my book. Of course, "hey dumb **** " is not better either, so people, if you see something that you don't like, don't insult other, but nicely tell them that you think what they said is not appropriate.

    As for RDRAM, I do not have anything to say that you didn't mention in your first post. Actually, you kind of answered yourself, yes it would be better. Of course, I am sure there is a reason because of which RDRAM is not (yet) used in vid. cards. Maybe someone with more knowledge on this can contribute some of it!

    By Angelus January 06, 2001, 06:37 PM

    I'm confused here.

    Isn't the RIMM module the actual piece of hardware? If so, of course that's the most expensive piece, it's THE piece you get.

    If it's only a part of the stick then why is
    the RIMM module the most expensive part? Is it made of something special maybe? I've never seen a RDRAM module for real, only in pictures.

    By H@rdw@reXpert January 06, 2001, 06:44 PM

    DDR is good enough on video cards today.

    By Elxman January 06, 2001, 07:23 PM

    That's very interesting, I think along the way video cards will be taking advantage of rdram's incredible bandwidth(just like what sony did with the ps2), and also what Arcadian has noted that it uses a 16bit datapath should make it more cheaper since there doesn't need to be as many traces. I know there is some downsides but I just can't think of it or I don't know how to explain.

    By James January 06, 2001, 07:41 PM

    quote:Originally posted by Angelus:
    I'm confused here.

    Isn't the RIMM module the actual piece of hardware? If so, of course that's the most expensive piece, it's THE piece you get.

    If it's only a part of the stick then why is
    the RIMM module the most expensive part? Is it made of something special maybe? I've never seen a RDRAM module for real, only in pictures.

    The "RIMM" (Rambus Inline Memory Module) is the PCB that the actual Rambus memory is mounted on. Same thing with SDRAM. SDRAM memory is currently mounted on a 168 DIMM (Dual Inline Memory Modules). So for example, if you talk about picking up a "stick" of 128MB of RAM, you are thinkind of purchasing a 168 DIMM with 128MB of RAM modules mounted on it. It is the mounting/packing of more memory in the same amount of space that ups the price of DIMMs as you increase the amount on a single DIMM. (aka 2x128MB sticks cost less than a single 256MB stick, etc.)

    Speaking of packaging: To follow along with the original discussion, how much RDRAM do you think could be theoretically packed onto the vid card's PCB? If video bandwidth is the current choke point, I would imagine another factor (not quite so serious at the moment) would be having to fetch data from system memory. Current SDRAM video memory on the Ultra series of nVidia cards runs what? 4.5 or 5 ns? What does main memory run at 7.5ns or something close to that?

    Also, just kind of an off the wall idea. Do you think that games will ever come to the point that all textures are loaded at the beginning of the game into the video cards cache. Throughout the entire game the video card would never have to load textures from main memory. The only data the video card would require for rendering is the current list of onscreen items and the textures that they use. Obviously, this would take a massive amount of onboard storage.

    Maybe not as technical as you would like, but better than "dumb***!"

    By AMD_Forever January 06, 2001, 10:23 PM

    There is one problem that rambus just created for themselves with getting their memory adapted to graphics cards. They went hostile on nvidia. In nvidias latest finance-technobable report they said rambus has requested royalties for the DDR ram nvidia graphics cards use. this could mean 1 thing, a) nvidia wins and pretty much is never friendly toward rambus or b) nvidia loses, has to pay more for DDR use than they would for rambus use and switch to using rdram. however, it's most likely nvidia will win and not want to deal with rambus at all. and as for me personally, i think rambus memory in graphics cards is a great idea, but with rambus pissing off chipset makers including intel and now pissing off video chipset makers, no one is gonna be considering them for anything no matter the technical gains.

    and on a final note, dont flame arcadian DAMNIT.

    By Adisharr January 06, 2001, 11:02 PM

    quote:Originally posted by Assmonkey:
    First off, i think you talk to much.
    second off, Yes RDRAM i think would be sweet, its just to expensive right now.

    Hmm.. let me guess.. 12 or 14 years old? Go to bed please..

    By dighn January 06, 2001, 11:20 PM

    jeez the guy just made a joke(although not funny) and you are all jumping on him... calm down ppl!

    By JabberJaw January 07, 2001, 12:22 AM

    quote:Originally posted by Arcadian:
    Many people believe that more memory bandwidth will allow for better frame rates, and faster graphics for very intense games.

    High end accelerators and 3D cards use memory for two distinctly different functions - for computation, and for the frame buffer.

    For computation, memory is used by the graphic processor like any microprocessor. Here is where the term "frame rate" you used actually refers to how many times per second the graphics engine can calculate a new image and put it into the video memory. Frame rate is much more a function of the type of software being used and how well it works with the acceleration capabilities of the video card. So, essentially what you are talking about doing here would be using RDRAM with a graphic processor in the same manner as used with some Intel microprocessors.

    For frame buffering, the bandwidth of the memory used to buffer video frame data to the RAMDAC is what affects the refresh rate per color depth per resolution. For example, at 1600x1200 Resolution, 24 Bit, 100 Hz Refresh, a video memory bandwidth of 549.3 megabytes/second is required. VRAM memory is considered best for frame buffering because it is dual ported for simultaneous write by GPU/read by RAMDAC. I'm not sure what effect RDRAM packet decoding would have interacting with the RAMDAC, but would suspect that any latency in this real-time function would be immediatly apparent on the monitor screen.

    Some cards use their video memory for both the frame buffer and additional calculations, and some have more than one type of video memory for the separate functions. Do you postulate using RDRAM for either, or both?

    By Fuzzball January 07, 2001, 02:09 AM

    Hmmmm. That's a lot to munch on. Gives me someing to ponder tonight. To be honest, I haven't been a Rambus fan, but you do present an interesting idea. It would be cool to see some real world benchmarks (hint hint to all relative the R&D departments out there)

    BTW, I don't think you talk to much. You gave a lot of info that was need and I give you credit for the time you spent on that post.

    By m538 January 07, 2001, 04:29 AM

    Bandwidth (Mb/s) is multiplication of bit width and frequency. You must understand that increasing of bit width and frequency hasn't same effect in certain cases. Actually increasing frequency with same latency is more effective but much more expensive than increasing bit width same times. In case with main memory CPU often need only 8,16,32 bits from entire 64,128,256-bit packet and next data from other place. CPU place-changing speed is limited by frequency. Programmers are trying to use continuous data to use increased bit width, but in most logical parts they can't do this so easy like with computation of angle array for example. But GPU uses much more continuous memory requests, it usually sends and takes packets up to 256-1024 bits.
    I'm trying to figure out that GPU doesn't need extra high-clocked memory like CPU. GPU itself isn't high-clocked enough, it's bit-wide, and if it will need more bandwidth it will utilize cheaper bit-wide memory instead of high-clocked. Even DDR technology has virtually double bit width not frequency.
    Last, video memory isn't a bottleneck. It's a bottleneck with current stupid situation that all textures stored in video memory. Memory bandwidth is high enough to support triple frame buffer and mipmap variables. I think video memory must also store more often used textures, but actually GPUs don't use cache mechanism applying to video memory. Program itself writes more used in the entire level/trace textures into local memory at the beginning of that level/trace.
    I suppose that with AGP 8x (with same bandwidth as 133 DDR RAM) we will finally see games with textures of one level more than 100Mb without video cards overcoming 64Mb memory and 1000$ barriers.

    By Humus January 07, 2001, 09:39 AM

    Well, I didn't read all post, but the topic is interesting. Graphic memory is actually a place where RDRAM would fit great (technologically, but I don't want to see it happend unless RAMBUS change their behaviour).
    A graphic card does almost always linear memory accesses. Many card uses tiled textures for increased linearity of the memory accesses. Latency is a very small problem but bandwidth is a important one.

    For cpu's I'd hope more for a low-latency technology such as FCRAM. A cpu accesses memory much more seldom in a linear manner.

    By Humus January 07, 2001, 09:49 AM

    quote:Originally posted by m538:
    Bandwidth (Mb/s) is multiplication of bit width and frequency. You must understand that increasing of bit width and frequency hasn't same effect in certain cases. Actually increasing frequency with same latency is more effective but much more expensive than increasing bit width same times. In case with main memory CPU often need only 8,16,32 bits from entire 64,128,256-bit packet and next data from other place. CPU place-changing speed is limited by frequency. Programmers are trying to use continuous data to use increased bit width, but in most logical parts they can't do this so easy like with computation of angle array for example. But GPU uses much more continuous memory requests, it usually sends and takes packets up to 256-1024 bits.
    I'm trying to figure out that GPU doesn't need extra high-clocked memory like CPU. GPU itself isn't high-clocked enough, it's bit-wide, and if it will need more bandwidth it will utilize cheaper bit-wide memory instead of high-clocked. Even DDR technology has virtually double bit width not frequency.

    Last, video memory isn't a bottleneck. It's a bottleneck with current stupid situation that all textures stored in video memory. Memory bandwidth is high enough to support triple frame buffer and mipmap variables. I think video memory must also store more often used textures, but actually GPUs don't use cache mechanism applying to video memory. Program itself writes more used in the entire level/trace textures into local memory at the beginning of that level/trace.
    I suppose that with AGP 8x (with same bandwidth as 133 DDR RAM) we will finally see games with textures of one level more than 100Mb without video cards overcoming 64Mb memory and 1000$ barriers.

    I agree with most except the last things. It's not a stupid situation that all textures are in video memory. AGP will never be fast enough for texturing. AGP speed is increasig slower than onboard memory speed.
    Also, GPUs does cache video memory. They have both texture cache and vertex cache. If you're programming with the texture cache in mind you can easily increase speed by a factor of two or close to that.

    By Arcadian January 07, 2001, 01:04 PM

    Wow, there is some really good discussion going on here. I appreciate everybody continuing to put their opinions in, even after the flames in the beginning (which I apologize for ).

    I see that some people are suggesting that memory bandwidth isn't as important as some other aspects of the video card. Can anyone elaborate on that, or give examples of ways that the GPU portion of the video card can be improved?

    Also, some people are suggesting that the latency of Rambus may affect the timing of the Ramdac and other refresh timings. Is there anything else fundemental that Rambus could cause problems with?

    Finally, a couple people mentioned Rambus politics, and that of course will also play a big part. Does anyone know of current legal battles with Rambus that could make a difference on whether video card manufacturers may adopt RDRAM as a video memory technology?

    Thanks again. This is good stuff... keep it coming.

    By Humus January 07, 2001, 06:52 PM

    quote:Originally posted by Arcadian:
    I see that some people are suggesting that memory bandwidth isn't as important as some other aspects of the video card. Can anyone elaborate on that, or give examples of ways that the GPU portion of the video card can be improved?

    My opinion: Memory bandwidth is the most important issue now.
    Even a Radeon (which is the least memory bandwidth constrained card among the newer ones) will choke if you don't carefully make sure that the GPU can all data it needs fast enough. You even have to think about such things as linearity as a developer to get good fps. I'm currently evaluating various rendering techiques for an upcoming 3dengine and in the current state of it it has 5 passes (normalmap, bumpmap, basetexture, lightmap and environmentmap). I got a strange experience with it during implementation of bumpmapping. The basetexture and the bumpmap are large textures (256x256 and higher is what I consider large in this case). The lightmap and normalmap are small (16x16).
    In the first implementation I rendered the bumpmap and basetexture in the same pass with multitexturing and got a fps of 90. But when I rendered it with two passes and single texturing I got 100fps. It was a little strange since the multitexturing should be twice as fast (if there were infinite memory bandwidth) and definitly not slower. Turning texture compression on made multitexturing score go up to 150 while single texturing went up to only 140. That revealed that memory held it back, and even more important linearity. With two large textures applied in the same pass the linerity is destroyed since it would need to fetch texels from two different places in memory for each pixel. After rearranging the passes to only have one large texture and one small texture in the same pass the fps went up to over 200 with texture compression on for the base texture (but not for the bumpmap since it doesn't look especially good compressed).

    By nkeezer January 08, 2001, 02:11 AM

    Given 3dfx's recent demise, and ATi's historical position as follower (as opposed to innovator), it seems to me that the only company that would be likely to introduce a Rambus video card would be Nvidia.

    Now, given the facts that 1) they were the first company to use DDR in a video card and 2) they were supposedly developing a DDR chipset, is it reasonable to assume that Nvidia has some kind of vested interest in DDR, or (maybe more likely) a reason to see Rambus to go down? If that's the case, I wouldn't expect to see Rambus in a video card for a while -- at least as long as Nvidia has the power that it does.

    quote:Originally posted by Arcadian:
    Finally, a couple people mentioned Rambus politics, and that of course will also play a big part. Does anyone know of current legal battles with Rambus that could make a difference on whether video card manufacturers may adopt RDRAM as a video memory technology?

    By m538 January 08, 2001, 04:23 AM

    I must add that I don't know future of course. If market wishes all textures will be loaded in the local video memory. Let this memory grows up to 4Gb or even more, IT IS NOT IMPOSSIBLE, but in such case engineers must develop protocol that virtually extend main memory with video memory to load textures directly without doubling them in two places. I think best choice is relatively cheap video card with maximum of 64Mb embedded memory and cool AGP.

    As I already posted somewhere, our eyes' resolution and framerate aren't endless. It seems that NV20 will support maximum resolution and framerate our eyes can see with current quality. It's still a lot of things to improve to make interactive games look like cinema. I think that majority of such improvement come from more powerful GPU and minority from increased AGP bandwidth. I didn't see T&L still, but I know it is an example. Certainly, I can be wrong there.
    Well, maybe 32-bit AGP 8x is not enough but PCI-X based 64-bit AGP 8x (4 Gb/s as dual channeled 133DDR) must be enough for a while.

    Also true quality come from large amount of textures and increased number of independent elements on the screen.

    By Humus January 08, 2001, 06:29 AM

    quote:Originally posted by nkeezer:
    Given 3dfx's recent demise, and ATi's historical position as follower (as opposed to innovator), it seems to me that the only company that would be likely to introduce a Rambus video card would be Nvidia.

    I wouldn't call ATi a "follower". There's nothing wrong with their capability to innovate. Rage128 was the best hardware when it can (but crappiest drivers seen by mankind) and Radeon is clearly the most innovative graphic product available until now.

    By Humus January 08, 2001, 06:36 AM

    I'd like to add ...
    What I'd like to see is better texture compression schemes. Compressed bumpmaps gives very weird results, thus makes texture compression useless on them. Some sort of texture compression that is created with bumpmaps in mind would be great. That's at least something that could boost performance in my 3dengine by 20%.

    By Moridin January 08, 2001, 11:18 AM

    I tend to agree with Arcadian. I think RDRAM is well suited to video cards. There seems to be some discussion about how much memory bandwidth is really required and whether or not it is really a bottleneck. This has been quite interesting and I am looking forward to seeing more on this. To me the correlation between bandwidth and video performance seems strong so I am guessing that it is important but I am no expert.

    My understanding is that video cards tend to use data in a very predictable way, and transfer large blocks of data at a time. This is where RDRAM really excels, since it's biggest problem is the initial latency. After the initial request is made RDRAM transfers data very quickly.

    QRSL RDRAM which has 3.2 GB/s on a 16-pin channel was announced last year although Rambus's web site lists it as being available in 2001. Maybe all this means is that although the technology is ready nobody is using it yet. Using QRSL and 128 data pins you could get 8*3.2=25.6 GB/s compared to 7 GB/s for the best DDR using the same number of pins. The restrictions on QRSL is that you can have a maximum of 4 devices on a 5 in channel. This should not be a problem for a video card.

    I suspect that RDRAM hasn't been used in video cards yet because of cost. The price of RDRAM has come down a lot recently but I think GPU makers have been reluctant to design around RDRAM while cost was high and availability was suspect, but if one company does I think others will follow suit. Graphics does seem to be one of Rambus's target markets.

    Further down the road I would like to see GPU's move towards embedded DRAM for memory this would provide the best possible bandwidth and latency. The only problems right now are cost of the special wafers required and the amount of die space required.

    By Arcadian January 08, 2001, 12:32 PM

    Moridin, not to mention that there is a limit to the amount of embedded memory that you can place on a die. The Playstation 2 and Game Cube are two examples. The PS2 could only fit 4MB of embedded SRAM, but that was on a .25u process, and SRAM tends to be much bigger and more expensive than DRAM. The Game Cube, which is on a .18u process using IBM's most cutting edge eDRAM process, only was able to fit 24MB of embedded memory on their chips. These amounts are certainly not enough for current video cards, which perform best at around 32MB-64MB. In the future, however, on .13u or better processes, we may see embedded memory start becoming available on video cards.

    By Moridin January 08, 2001, 01:58 PM

    quote:Originally posted by Arcadian:
    Moridin, not to mention that there is a limit to the amount of embedded memory that you can place on a die. The Playstation 2 and Game Cube are two examples. The PS2 could only fit 4MB of embedded SRAM, but that was on a .25u process, and SRAM tends to be much bigger and more expensive than DRAM. The Game Cube, which is on a .18u process using IBM's most cutting edge eDRAM process, only was able to fit 24MB of embedded memory on their chips. These amounts are certainly not enough for current video cards, which perform best at around 32MB-64MB. In the future, however, on .13u or better processes, we may see embedded memory start becoming available on video cards.

    Yes, that is what I was getting at with limited die space. The primary benefit of EDRAM is it takes much less space then SRAM therefor you can get more on a chip. I decided to start a new thread on EDRAM and I would be interested in hearing your thoughts on potential uses for this technology.

    By Marsolin January 08, 2001, 07:44 PM

    It think that RDRAM is very well suited for video memory. One detriment though is density. SDRAM technology typically seems to be one generation ahead of RDRAM. 512Mb is available for DDR, but RDRAM is still 256Mb.

    I agree with Arcadian that the 1 GB/s is conservative. Cypress released a 533MHz DRCG (Direct Rambus Clock Generator) a few months ago that I assume would be ideal for these situations.

    I have also heard rumors about the quad-pumped RDRAM that was mentioned above and it would be a logical progression. I think the proposed 8 channels of RDRAM to match the bit width of DDR would probably be pared down and the clock speed increased to account for the needed speed. Eight channels of RDRAM would take more space to route than 2 channels of DDR, even though the graphics chipset pin count would be the same.

    By 3dcgi January 08, 2001, 11:23 PM

    Despite one earlier post memory bandwidth is definitely a problem with graphics performance. Its effect will vary depending on the chip's architecture and every chip on the market today is affected by a lack of bandwidth. For proof look no further than benchmarks of nVidia's chips. Increasing memory clock speed boosts performance tremendously.

    Designers have attacked this problem with techniques like texture compression, z buffer wizardy (ATI's hyper z), and embedded dram among others. Embedded dram has so far been tried with limited success and it will probably be a while longer before it becomes mainstream. If it ever does. We have yet to see a product from BitBoys despite their promises of embedded dram. The best use of embedded dram might be as a supplement to DDR or RDRAM. Maybe as a level 2 or 3 cache. I also expect companies to start using some form of vertex or geometry compression.
    Why should textures get all the attention? Polygons take memory too.

    I don't know why RDRAM is not being more widely used, because there could be some advantages. Many people are saying that RDRAM is too expensive and that may be so, however RDRAM needs less pins for bandwidth equivalent to DDR which means the chip's die is smaller and less expensive. This is also one reason why DDR is used instead of just slapping more SDR chips on a board. Smaller is better.

    Technical risk and expertise might be a downside to using RDRAM. Intel has shown that designing chipsets and interfaces is difficult. Just look at all the problems with 820. Graphics companies are already coming out with new designs in as little as 6 months. Totally changing the architecture of the memory controller might be too risky.

    By m538 January 09, 2001, 02:11 AM

    Originally posted by Humus:
    Also, GPUs does cache video memory. They have both texture cache and vertex cache.
    ----------
    I hadn't found information what GPU does cache video memory, or I understood you incorrectly. I know that GPUs have small on-die cache. And I mean that GPU must use a part of local video memory to cache textures which basically stored in the main memory. Did you say that GPU does this without program help? If so, I will think about current situation as pretty good one.

    My last knowledge about NV20 that it will have 200DDR/256 memory and 300/256 chip, while GeForce2pro has 200DDR/128 memory and 200/256 chip, and GeForce2ultra has 233DDR/128 memory and 250/256 chip. I think nVidia engineers are smart enough and adjust their product for optimal performance. See, even they can make video card with 233DDR/128 memory and 200/256 chip, they didn't. They don't think video memory to GPU bandwidth is a bottleneck. Instead they develop AGP 8x even you said it is a shame.
    Evaluation:
    ( GeForce2pro memory bandwidth ) / ( GeForce2pro chip bandwidth ) = 1
    while
    ( NV20 memory bandwidth ) / ( NV20 chip bandwidth ) = 1.333
    "Aha!", you say, "video memory is a bottleneck". But NV20 will be clock-to-clock faster.
    Once again (sorry people) video memory is a bottleneck when all textures are loaded in it and you are comparing framerates above 100. But it is not the way video card must work. I am sure nVidia adjust chip/memory equation for games with textures and polygons (as 3dcgi significantly added) which take at least twice as entire video memory. People, that's right point.
    Probably when GPUs will reach 500 MHz, RDRAM will be MUST. I still think that video cards don't need high-clocked RDRAM at this time and are satisfied with bit-wide DDR RAM.

    By Humus January 09, 2001, 04:11 AM

    quote:Originally posted by m538:
    I hadn't found information what GPU does cache video memory, or I understood you incorrectly. I know that GPUs have small on-die cache. And I mean that GPU must use a part of local video memory to cache textures which basically stored in the main memory. Did you say that GPU does this without program help? If so, I will think about current situation as pretty good one.

    Games don't need to take care about memory management, that's something for the driver (at least in OpenGL and DirectX, but not in Glide). You just call a texture uploading function that is part of the API. In OpenGL it's called glTexture2D(). All the application needs to keep track on is the ID for that texture, but the driver decides what textures will be resident in video memory. As a developer you try to fit everything into video memory, because transfers over AGP each frame will kill performance.


    quote:Originally posted by m538:
    My last knowledge about NV20 that it will have 200DDR/256 memory and 300/256 chip, while GeForce2pro has 200DDR/128 memory and 200/256 chip, and GeForce2ultra has 233DDR/128 memory and 250/256 chip. I think nVidia engineers are smart enough and adjust their product for optimal performance. See, even they can make video card with 233DDR/128 memory and 200/256 chip, they didn't. They don't think video memory to GPU bandwidth is a bottleneck. Instead they develop AGP 8x even you said it is a shame.
    Evaluation:
    ( GeForce2pro memory bandwidth ) / ( GeForce2pro chip bandwidth ) = 1
    while
    ( NV20 memory bandwidth ) / ( NV20 chip bandwidth ) = 1.333
    "Aha!", you say, "video memory is a bottleneck". But NV20 will be clock-to-clock faster.
    Once again (sorry people) video memory is a bottleneck when all textures are loaded in it and you are comparing framerates above 100. But it is not the way video card must work. I am sure nVidia adjust chip/memory equation for games with textures and polygons (as 3dcgi significantly added) which take at least twice as entire video memory. People, that's right point.
    Probably when GPUs will reach 500 MHz, RDRAM will be MUST. I still think that video cards don't need high-clocked RDRAM at this time and are satisfied with bit-wide DDR RAM.

    Whatever you think you know about NV20, it's probably not gonna be final specs. Any, sure they didn't release GTS with lower clockspeed. Why would they reduce the clockspeed just because memory is slower? That will just lower the performance during not so memory intensive operations, such as flatshading or texture magnification.

    And AGP8x won't be available on NV20, the first AGP8x products are expected to come 2003.

    By Arcadian January 09, 2001, 10:58 AM

    quote:Originally posted by m538:
    Originally posted by Humus:
    My last knowledge about NV20 that it will have 200DDR/256 memory and 300/256 chip, while GeForce2pro has 200DDR/128 memory and 200/256 chip, and GeForce2ultra has 233DDR/128 memory and 250/256 chip. I think nVidia engineers are smart enough and adjust their product for optimal performance. See, even they can make video card with 233DDR/128 memory and 200/256 chip, they didn't. They don't think video memory to GPU bandwidth is a bottleneck. Instead they develop AGP 8x even you said it is a shame.
    Evaluation:
    ( GeForce2pro memory bandwidth ) / ( GeForce2pro chip bandwidth ) = 1
    while
    ( NV20 memory bandwidth ) / ( NV20 chip bandwidth ) = 1.333
    "Aha!", you say, "video memory is a bottleneck". But NV20 will be clock-to-clock faster.
    Once again (sorry people) video memory is a bottleneck when all textures are loaded in it and you are comparing framerates above 100. But it is not the way video card must work. I am sure nVidia adjust chip/memory equation for games with textures and polygons (as 3dcgi significantly added) which take at least twice as entire video memory. People, that's right point.
    Probably when GPUs will reach 500 MHz, RDRAM will be MUST. I still think that video cards don't need high-clocked RDRAM at this time and are satisfied with bit-wide DDR RAM.

    Assuming your knowledge of the NV20 is correct, don't you think that a lot of clever routing has gone into increasing the bit width of the memory bus to 256 bit? You claim that the DDR channel will be 200MHz and 256 bit wide. If they used the quad data rate Rambus, they could have made it 64 bit wide, running at 400MHz QDR, and make a much cheaper video card for the same bandwidth, and perhaps equal engineering work (of course this is a qualitative opinion, since I would not know how hard it is to implement quad data rate Rambus relative to routine 256 bits of DDR data).

    Or, they could have made a slightly cheaper solution using standard double data rate Rambus with 128 bits of data, and using the new clock generator that someone mentioned at 533MHz. This would make 533 * 2 * 2 * 8 = 17GB/s bandwidth, which is much more than the DDR solution of 200 * 2 * 8 * 4 = 12.8GB/s. (The numbers come from the clock speed of the memory, the number of data bits per clock (DDR or QDR), the width of the data in bytes, and the number of channels necessary for 128 bits and 256 bits, respectively).

    Overall, RDRAM would still have made a better solution. However, the caveats include more work being spent perfecting a new technology, inherent problems in the design that could cause timing inconsistancies or other bugs, Rambus politics, and many other reasons. I'm sure nVidia has their own reasons for not choosing it, but it does remain that it could have made a better, cheaper solution.

    By Galen_of_Edgewood January 09, 2001, 12:23 PM

    Rambus is killing itself by all of the lawsuits against possible partners. Sueing(sp?) Nvidia was probably one of Rambus' biggest mistakes.

    I do not personally see Rambus winning it's lawsuits. If this is true, I would highly doubt that Nvidia will support a former enemy because of the bad blood of the law suit.

    I do agree with you, Arcadian. Rambus' memory would go very well with video cards, but I do not see it happening unless Rambus wins all of its lawsuits. It will be the cheapest memory at that point in time and no other option of making video cards priced in that "sweet spot" would be possible, w/o the use of RDRAM.

    Here is another aspect to this that I was curious about. What about the amount of power that is required to keep the memories running? Is RDRAM more expensive than SDRAM or DDR SDRAM in terms of power?

    Then again, I've seen talk about an AGP Pro slot. Will this supply all of the power needs of a video card for a while?

    Another wrinkle that just popped into my mind. (Sorry, my mind is just rambling on over here.) What about the heat spreader that is located on the RDRAM chips? Will this be anymore of a problem/cost for the video card manufactuers to consider on their design of their video cards?

    By Marsolin January 09, 2001, 06:58 PM

    quote:Originally posted by Galen_of_Edgewood:
    Rambus is killing itself by all of the lawsuits against possible partners. Sueing(sp?) Nvidia was probably on of Rambus' biggest mistakes.

    Bad PR from all of these suits is a big problem for Rambus. Despite having a great technology DDR will probably win as long as it remains close in performance because no one likes Rambus.

    quote:Originally posted by Galen_of_Edgewood:
    Here is another aspect to this that I was curious about. What about the amount of power that is required to keep the memories running? Is RDRAM more expensive than SDRAM or DDR SDRAM in terms of power?

    Then again, I've seen talk about an AGP Pro slot. Will this supply all of the power needs of a video card for a while?

    AGP Pro allows about 110W of power. And that should be plenty of headroom for a while.

    By Un4given January 11, 2001, 05:21 PM

    One of the main problems I see with RDRAM is the memory controller side of things. Now I'm not an engineer, but if you look at what it took Intel to get a decent performing Rambus chipset, that is a lot work.

    Right now the dual channel Rambus solutions are putting out 3.2GB/sec. Now even if you go quad channel, you get 6.4GB/sec, which is about right on par with a GF2 Pro. The more channels you add, the more complex the memory controller becomes.

    Also keep in mind that QDR SDRAM is on the horizon.

    Lastly, I do believe that memory is the biggest bottleneck. I also think that tile based rendering or other HSR techniques would be a better idea than trying to continually increase memory bandwidth via RAM only. By reducing or eliminating overdraw, and substantial amount of memory bandwidth is conserved.

    By Arcadian January 11, 2001, 08:42 PM

    quote:Originally posted by Un4given:
    One of the main problems I see with RDRAM is the memory controller side of things. Now I'm not an engineer, but if you look at what it took Intel to get a decent performing Rambus chipset, that is a lot work.

    Right now the dual channel Rambus solutions are putting out 3.2GB/sec. Now even if you go quad channel, you get 6.4GB/sec, which is about right on par with a GF2 Pro. The more channels you add, the more complex the memory controller becomes.

    Also keep in mind that QDR SDRAM is on the horizon.

    Lastly, I do believe that memory is the biggest bottleneck. I also think that tile based rendering or other HSR techniques would be a better idea than trying to continually increase memory bandwidth via RAM only. By reducing or eliminating overdraw, and substantial amount of memory bandwidth is conserved.

    Actually, the small pin count, and packate based data transfer allow RDRAM to lend itself to multiple channels. There is no reason that I can see not to go with 8 channels for a video card. The routing of data pins will be no more complicated than for SDRAM. In fact, Rambus designed their technology around multiple channels, so adding more RDRAM channels does not complicate the memory controller nearly as much as adding more pins for SDRAM (as video cards currently do).


    Contact Us | www.SharkyForums.com

    Copyright © 1999, 2000 internet.com Corporation. All Rights Reserved.


    Ultimate Bulletin Board 5.46

    previous page
    next page





    Copyright © 2002 INT Media Group, Incorporated. All Rights Reserved. About INT Media Group | Press Releases | Privacy Policy | Career Opportunities