Almost a year ago I’ve wrote post about 5970 and this week I’ve finally grabbed 6990 for tests by my own. As title states:

Same ruler, almost the same size as 5970. I’ve already had several tests results from 6990 owners and they looks kinda weird — while 6990 was faster than 5970 it still was slower than my expectations. First tests by my own produced values like:

That’s 10% slower. I’ve tested with SHA1 kernels, SL3, Office 07-10, WPA — everything were slower than expectations. I’ve grabbed my old program to measure GFLOPS of ATI GPUs and started series of experiments.  Apparently lowering GPU core frequency resulting in “closer to estimations” performance. My first guess was that there is internal throttling in 6990 and so overheating causing performance drop. I’ve even posted in official forum about this but some more experiments reveals that I wasn’t totally true. Answer was pretty simple:

Yep, by default it isn’t enough power provided for 6990 to make it work with 100% performance! This adjust results in:

Thus, power usage for 2nd core must also be tweaked and we’ll see:

At last the value I was expecting! Apparently, 5s running time is not good enough for precise measurements, so I’ve increased charset size and, well, hardware monitoring value as it reaching 90C in no time (and 95C is also happens very soon).

Mystery solved. My several months old estimations were correct.

If you’re going to repeat above steps with your 6990 make sure you have proper cooling and PSU as looks like official 375W TDP can easily became 450W and this means A LOT of heat you’re need to deal with somehow.

Latest ighashgpu can be downloaded here.