What about the specifications? It's quite a surprise; the HD 3870 X2 clock strays away from the HD 3870. But it's a mixed blessing. The GPU is fully clocked at 825 MHz, meaning 50 MHz or 6% better than the 3870. This is quite an accomplishment, especially compared to the 7950 GX2 that had seen its clocks decrease compared to the 7900 GTX. On the other hand, the gigabyte of GDDR3 found on the HD 3870 X2 is clocked at 900 MHz, compared to 1125 MHz on the HD 3870 (that uses GDDR4) and 1080 MHz on the 8800 Ultra. Fortunately, the memory interface reaches 512 bits, which gives a bandwidth slightly superior to that of the 800 Ultra. Let's note however that it's more appropriate to consider this card as equipped with 2 x 512 MB, each GPU working with its own frame buffer. Thus it means this limited amount could be another bottleneck in high resolutions, which we'll verify later on.
|GPU||HD 3870 X2||HD 3870||8800 Ultra|
|GPU Clock||825 MHz||775 MHz||612 MHz|
|Shaders Clock||825 MHz||775 MHz||1512 MHz|
|Memory Clock||900 MHz||1125 MHz||1080 MHz|
|Width of the memory bus||512 bits||256 bits||384 bits|
|Amount of memory||2 x 512 MB||512 MB||768 MB|
|Number of Pixels/Vertex Pipelines||(160)||(80)||(32)|
|Number of texturing units||32||16||32|
|Number of ROP||32||16||24|
|Throughput 1 TFlops||496 GFlops||387 GFlops|
|Memory Bandwidth||115.2 GB/s||72 GB/s||103.7 GB/s|
|Number of transistors||1334 million||666 million||754 million|
|Die's surface||2 x 196 mm²||196 mm²||484 mm²|
|Supported Shader Model||4.1||4.1||4.0|
Bugs and Drivers
Without going so far as to call it the faithful heir to the Rage Fury MAXX, we've come across some bugs while using the (beta) drivers. First of all, they often refused to install, stating that we needed to be logged in as administrators (which, of course, we were). The message disappeared after a reboot. Three games have also presented problems. For Test Drive Unlimited and STALKER, changing to another resolution (whatever the resolution) would cause the screen to blink as if it were refreshing at 30 MHz. The problem disappeared as fast as it came, simply by changing the resolution again. As for World In Conflict, the blinking was stronger and irreversible and would be limited to the games' map. The other games didn't suffer from any problems. Finally, it appeared that 2D rendering in Windows XP occasionally became partially or very blurred.
Those bugs really remind us of those encountered during the CrossFire test, but also of the GeForce 7950GX2 review ... They're also the reason why the HD 3870 X2 embargo was delayed (it was originally supposed to be lifted last wednesday). AMD wanted to release new drivers at the last minute, the 123a. These drivers didn't solve any bugs and haven't changed the performance. A few occasional drops where noticed, the most significant ones appearing once antialiasing was activated (in Oblivion or Age Of Empires III). There was no change in picture quality. Thus, we stuck with the 108a drivers for all the cards, as they've been the best in our experience.