The war between dual core converts and single core enthusiasts has been going on since the first dual core processor rolled off the line. One side appreciates the seamless multi-tasking and super multi-threaded performance, while the other expresses disdain for anything less than the top single-threaded gaming performance. AMD helped nurture this along, as the company would release a powerful dual core model that helped bridge the gap, but follow that up with an even faster Athlon 64 FX single core model. This ended with the 2.6 GHz Athlon 64 FX-60, which took the FX line to dual core, but it still existed somewhat in the shadow of the 2.8 GHz Athlon 64 FX-57. That shadow has been cast aside by the new Athlon 64 FX-62, which also sports a 2.8 GHz core speed and a dual core design. The 2.6 GHz Athlon 64 X2 5000+ comes along for the ride, as AMD introduces the Socket AM2 platform and its support of high-speed DDR2.
AMD's newest powerhouse may look like a simple core speed increase on the outside, but there have been significant changes made to the Athlon 64 FX-62. But chicks dig core speed, so 2.8 GHz of dual core power will certainly turn a few heads, not to mention finally dropping the 2.8 GHz Athlon 64 FX-57 single core from consideration. The 2.8 GHz clock speed is combined with a 2x1-MB dual core architecture, which follows right in line with the previous Athlon 64 FX-60. It also includes 64K of L1 instruction and 64K of L1 data cache (per core), for a total of 256KB of L1. The processor runs on a core voltage of 1.35V-1.4V, has a thermal power rating of 125W, and includes 227.4 million transistors.
The Athlon 64 X2 5000+ is a different architecture and sports a 2.6 GHz clock speed and uses a 256K L1 and 2x512-MB L2 design, which is part of the Athlon 64 X2 4600+ and 4200+ line. This seems to be the direction AMD is moving in, keeping this 2x512-MB core format for the Athlon X2 line, while transitioning the "old" Athlon 64 X2 4800+/4400+ 2x1-MB architecture for the new Athlon 64 FX processors. The smaller L2 cache also translates into a smaller processor die, and the Athlon 64 X2 5000+ includes 153.8 million transistors and has a thermal power rating of only 89W, while dropping the core voltage to the 1.3V-1.35V range. The release of the 2.6 GHz Athlon 64 X2 5000+ may not get the press of the Athlon 64 FX-62, but for those who want a cooler-running, more energy-efficient powerhouse, this is the place to go.
The big change for these Socket AM2 processors is the addition of an onboard DDR2 memory controller, with support up to dual channel DDR2-800 speeds. This new socket offers an incredible 12.8 GB/sec. of memory bandwidth at the top end, and this kind of headroom will allow AMD to increase core speeds with ease, which is especially important once the 65nm milestone is reached. AMD has not made the move to 65nm yet, so these are both 90nm parts, although it is a new "F" core revision. Socket AM2 models also support AMD Virtualization technology, although the software support is still in is infancy. AMD has also re-released a whole line of updated Socket AM2 Athlon 64 X2, Athlon 64, and Sempron processors (along with more expensive 65W and 35W models), which not only maintain the same model numbers, core speed and cache levels of their Socket 939 counterparts, but are priced competitively as well.
Socket AM2 is AMD's answer to a unified platform, and brings the high-end, mainstream and entry-level processors under one roof. There will be no more single/dual-channel memory controllers, no more 754-pin vs. 939-pin sockets, just a one-size-fits-all platform for the entire spectrum of AMD processors. Socket AM2 is a 940-pin format, and to make absolutely sure no one tries to install the wrong processor, is keyed (one open pin square vs. two) to insure only AM2 models make the grade. Along with the obvious upgrade possibilities, the main benefit is that every new AMD processor, from the Athlon 64 FX down to the Sempron, will now include a dual channel DDR2 memory controller. Of course, AMD still needs to differentiate based on target market, so the Athlon 64 FX and X2 models will offer DDR2-800 support, while the other Athlon 64 and Sempron processors max out at dual channel DDR2-667.
Another nice change is the addition of a more robust heatsink attachment, which has now been mounted on the motherboard using 4 screws and allows a bit more helf to your heatsink. The basic design has remained consistent, and although the Socket is slightly different, some older Socket 939 heatsink-fan units may actually fit. Obviously, a new motherboard is required, and our reference processor came with an ASUS nForce 590 SLI motherboard, which is part of the new nForce 500 Series of motherboard chipsets. These include the NVIDIA nForce 590 SLI (2x16x PCIe), NVIDIA nForce 570 SLI (1x16x, 2x8x PCIe), NVIDIA nForce 570 Ultra (performance), and NVIDIA nForce 550 (mainstream).
You could almost say that the Athlon 64 architecture was built for DDR-400. The processor features a 200 MHz base clock generator, which the processor multiplier then uses to derive overall clock speed in an X times 200 format. The processor then divides its operating frequency by a whole number to determine the memory frequency. As these are synchronous at DDR-400 levels, there was never any issue with Socket 939. DDR2 brought a whole new level of complexity to AMD memory frequencies, as these are no longer tied to the standard 200 MHz DDR clock speed, but rather the 266 MHz, 333 MHz, and 400 MHz clocks of DDR2-533, -677 and -800, respectively. Like DDR, these are the base clock rates that are then "doubled" internally to their rated speed, but the actual memory dividers are unable to match up the exact DDR2 clock speed in some cases, which results in non-standard clock speeds.
This translates into the following memory speeds for 2.8 GHz Athlon 64 FX-62 (14x200) and 2.6 GHz Athlon 64 X2 5000+ (13x200):
So basically, the Athlon 64 FX and X2 models with even multipliers support DDR2-800 dead on, while the odd numbered models run at a lower speed. Of course, the opposite is true at DDR2-667, and the odd numbered processors get closer to the actual speed. Exactly how this impacts performance is still open game, but from our benchmarking, it doesn't seem to have much effect at all. We ran through a variety of memory and system tests using different processors and memory speeds, and had planned to publish them, but to be honest, there was virtually no discrepancy at DDR2-800 and only a slight gap at DDR2-667.
From these results, we're assuming that the extreme bandwidth present with dual-channel DDR2-800 is more than enough to handle the processor's requirements, and in most cases, the remainder goes unused. Dual-channel DDR2-800 yield a maximum bandwidth of 12.8 GB/sec., while many of the memory benchmarks are only in the 8 GB/sec. range, which lends at bit more weight to this theory. Either way, this is not something anyone should lose sleep over, as performance is consistent in both DDR2-800 configurations.