The high-end video card market consists of many different buyer types, from those who seek out the very best price-performance ratio, to others who look for the absolute highest performance, and let their wallet be damned. In between these two extremes exists the buyer who weighs the entire mix of features, upgradeability, performance, and value, while still looking for the best high-end video card within a set budget. ATI has a few options in their Radeon X1950 and X1900 lines that match this criteria, and this review will examine one of them, the Radeon X1900 XT 512MB. This card is not the fastest, but neither is it the most expensive, and its mix of features and CrossFire upgradeability still makes it a compelling high-end graphics choice.
The Radeon X1900 XT 512MB card features the 90nm R580 core, which follows along with the current ATI strategy of placing overall pixel shading at the forefront of the architecture. This is easy to see from even a cursory examination of the specs, as the R580 features 16 pixel pipelines, 16 texture units and 8 vertex pipelines, but a whopping 48 pixel shaders. The R580 consists of 16 pixel pipelines (or 4 pixel quads) each with 3 pixel shaders per pipe. This gives the Radeon X1900 XT an incredible amount of pixel shading power, and allows for extremely high performance levels with the right game or application. This design is similar to the Radeon X1600/X1650, but on a much higher scale. The ATI card's memory architecture is standard for the class, and consists of a 256-bit, 8-channel path to 512MB of GDDR3 memory, powered by a Ring Bus memory controller.
ATI has another notable advantage compared to the NVIDIA cards, and it comes in the form of high core and memory clock speeds. The Radeon X1900 XT 512MB runs at 625 MHz core and 1.45 GHz memory, while its Radeon X1900 XTX 512MB sibling is set slightly higher at 650 MHz core and 1.55 GHz memory. These clock speeds translate into some incredible fillrate and memory bandwidth specifications. The Radeon X1900 XT 512MB sports fill rates of 10.0 GTexels/s and 10.0 GPixels/s (10.4 GTexels/GPixels/s for the Radeon X1900 XTX), along with a memory bandwidth of 46.4 GB/s (49.6 GB/s for the Radeon X1900 XTX). The 3 pixel shaders per pipeline also means that the GTexels/s (shaded) fillrate is theoretically triple that of the standard results. These specifications place the Radeon X1900 XT 512MB right near the top of the single-card/GPU performance ladder, behind only the Radeon X1900 XTX and X1950 XT/XTX on the ATI side.
The basic format of the ATI Radeon X1900 XT 512MB card is similar to the high-end X1800 XT boards, and features a dual slot design using a PCI Express x16 interface. The size of the cooling hardware is quite impressive, and the ATI Radeon X1900 XT 512MB is a bit heavier and longer than a comparable NVIDIA card. Surprisingly, this doesn't translate into higher noise levels, as the larger fan and heatsink made operating levels during our testing quite low, and the only real negative is the potential loss of an adjacent PCIe/PCI slot. Naturally, the ATI card utilizes the default clock speeds of 625 MHz core and 1.45 GHz memory, so there are no surprises on that end.
In terms of physical design, the ATI Radeon X1900 XT 512MB features a white, ATI-branded heatsink-fan, with dedicated fan port on the card's backplate. The remainder of the backplate is fairly standard, and includes dual integrated dual-link DVI ports and an S-Video/Video-In/Video-Out port. ATI includes a Xilleon TV encoder for high-end video output, as well as full SDTV support up to 525i and HDTV support up to 720p/1080i (using YPrPB component output). The ATI card requires external power, and includes a standard 6-pin PCI Express connector on the outside edge. The ATI Radeon X1900 XT 512MB can handle all resolutions up to 2560x1600 for DVI and 2048x1536 for analog/VGA. The card is also CrossFire compatible, and offers support for HDR, Shader Model 3.0, and Avivo.
To give a better idea of the architecture of the various mainstream and high-end cards we see competing directly against the ATI Radeon X1900 XT, here is a small chart outlining the key architectural features of each GPU:
Graphics
Processor
Pixel
Pipes
Pixel
Shaders
Texture
Units
Vertex
Pipes
ROPs
Radeon X1600 XT
4
12
4
5
4
GeForce 7600 GT
12
12
12
5
8
GeForce 6800 GS
12
12
12
5
8
Radeon X1800 XL
16
16
16
8
16
Radeon X1900 GT
12
36
12
8
12
Radeon X1950
Pro
12
36
12
8
12
GeForce 7800 GT
20
20
20
7
16
GeForce 7900
GT/GTX
24
24
24
8
16
Radeon X1900
XT/XTX
16
48
16
8
16
Keep in mind that as many graphics designs have taken a modular view of the architecture, so the entire picture of the GPU needs to be taken into consideration. No more is performance relegated to the number of pixel pipelines or texel processing, but pixel and vertex shaders need to be taken into account, as does the number of ROPs (or Render Output units). Of course, the best performance metric is real-world testing, and to that end, we've assembled a wide range of game benchmarks in the next section.
