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ATI Radeon HD 3870 X2 - Fastest Yet!

Specifications

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.

Cards Specifications
GPUHD 3870 X2HD 38708800 Ultra
GPU Clock825 MHz775 MHz612 MHz
Shaders Clock825 MHz775 MHz1512 MHz
Memory Clock900 MHz1125 MHz1080 MHz
Width of the memory bus512 bits256 bits384 bits
Memory typeGDDR3GDDR4GDDR3
Amount of memory2 x 512 MB512 MB768 MB
Number of Pixels/Vertex Pipelines(160)(80)(32)
Number of texturing units321632
Number of ROP321624
Throughput 1 TFlops496 GFlops387 GFlops
Memory Bandwidth115.2 GB/s72 GB/s103.7 GB/s
Number of transistors1334 million666 million754 million
Process0.055µ0.055µ0.090µ
Die's surface2 x 196 mm²196 mm²484 mm²
Generation200820072007
Supported Shader Model4.14.14.0

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.