AMD/ATI RV6x0 VGA cards shootout
Author: Luka Rakamaric
Date: 23 Aug 2007

AMD introduced four new cards to its DirectX 10 lineup a little less than two months ago, aiming to compete with NVIDIA's 8600 and 8500 series cards. Today we are reviewing a bunch of 2400 and 2600 series cards, with some of them being custom models from ATI's partners. ATI's 2400 and 2600 series cards came to the market later than 8600 and 8500, but they did fail to live up to the expectations, and all models performed worse than direct NVIDIA competitors. This prompted ATI to reduce the prices immediately, making their cards more desirable.

First let?s take a look at the weaker of the two GPUs. The 2400 series is based on a R600 derivate called RV610. Compared to the R600 chip, it is quite tiny. The R600 has four SIMD units, and each of them has 16 execution units, all counting up to 320 stream processors (4x16x5). The RV610 is much smaller. It only has two SIMD units, with four execution units each, coming up to 40 stream processors (2x4x5). ATI also left only one texture unit and one render back-end. The result is a GPU that has around 70 million transistors, and thanks to the 65 nm production process it only measures 7 mm by 10 mm, which is also an interesting format considering that it is a rectangle rather than a square. In comparison, the G86 GPU has around 210 million transistors and 132 mm2, more than double the transistors and almost double the area. Despite its size, it has full DirectX 10 support, and even some extras not present on the R600 flagship. They are called ?Avivo HD? and UVD, or universal video decoder. UVD does important decoding for codecs like H.264 and VC-1, lowering the CPU load. This is however the case with NVIDIA as well, so these features only level the playing field between NVIDIA and ATI in this segment. The RV610, however, can only produce four sample antialiasing, although this can be extended using CFAA, or custom filters such as narrow-tent or wide-tent.

We had three cards based on this GPU, Sapphire 2400XT with 256 MB GDDR3 memory, PowerColor 2400Pro with 256 MB DDR2 memory and ASUS 2400Pro with 256 DDR2 memory.

Sapphire card?s GPU operates at 700 MHz, the same as with its GDDR3 memory. The card itself is based on ATI?s reference design. The same can be said for PowerColor?s 2400Pro, only the clocks are different. The 2400Pro GPU operates at 525 MHz and the DDR2 memory at 400 MHz. Unlike the former two cards, the ASUS 2400Pro is based on a custom PCB design. However, we were unable to get two of these cards to work in CrossFire mode.

The second GPU we have powering the cards is the RV630, also a derivate of the R600. It has three SIMD units with eight execution units each, counting up to 120 stream processors. The GPU also has two texture units, but only one render back-end, the same as the weaker RV610. As a result it can filter eight texels and put out four pixels per clock. When compared to the competition, ATI is a little sluggish, as the G84, or 8600 can produce almost double that. RV630 is comprised of 390 million transistors, which is a lot more than the G84, which has 289 million. The surface area of the RV630 is 155 mm2, something less than 169 mm2 of the G84, all thanks to the 65 nm production process.

Sapphire 2600XT with GDDR4 memory, Gigabyte 2600XT with GDDR4, PowerColor 2600 Pro with DDR2 and ASUS 2600 Pro with DDR2 all use the RV630, but with different clocks. XT variants with GDDR4 memory have a core clock of 800 MHz and memory clock of 1100 MHz. Models with GDDR3 memory, which we didn?t get for this review have a memory clock of 700 MHz, which is quite a lot less.

For benchmarking purposes we used our standard testbed configuration:
- Intel Core 2 Duo E6700
- EVGA 680i SLI
- OCZ Platinum PC2-8000, 2x1GB @ 800 4-4-4-12
- OCZ GameXstream 1010W
- Western Digital RaptorX 150 GB

Since we had a few double cards, we also had a DFI ICFX-3200 T2R/G Crossfire motherboard for that portion of the test. Some of these are low end or mainstream cards, we benchmarked the cards using the 1440x900 resolution, which is almost identical to the 1280x1024 resolution in terms of pixels, but is used on the growing wide screen LCDs market.

We compared the cards to the NVIDIA competition, 8500GT and 8600GT and GTS.