wingless
02-01-09, 03:00 PM
Apparently current GPU2 WUs just happen to be fast on Nvidia's less complex hardware at the moment. ATI GPUs are currently heavily limited in performance, all according to this guy from TR:
Okay about ATI Vs. Nvidia.
For low end cards, get Nvidia, they definitely out do anything that is currently offered by ATI, mainly because they aren't much improvement compared to the 3850 which is used for benchmarking, and thus sit around the 1.5k ppd area.
However, if you did have the money, it might be best to think twice about choosing Nvidia over ATI. Sure the GTX 260 gets 7-9k ppd, and the HD 4870 only gets 4-5k, but its important to understand how points are assigned.
The benchmark machine is a Radeon HD 3850, points are determined so that no matter what WU the 3850 does, it will get 1.5k ppd per day. For instance all those 511 point WU's the 3850 will do three per day or so. Pretty basic, yes?
Now, Nvidia does well because the current range of WU's are in-efficient on ATI gpus. All gpu work units are very small at the moment, (You know how when you select WU size, you have the option of small, medium, or large? There only are small WU's and a few medium ones out yet) this is due to the GPU client still being early days. So Nvidia cards are essentially optimized for this kind of WU, they have a smaller amount of fast shaders. This is compounded by the fact that the ATI client has huge in-efficiencies so that it can't use any more shaders than were on the HD 3870.
So where am I going with this.
1. Once larger WUs are released, ATI gpus will do much better as they are more suited to this with the greater amount of shaders. Nvidia gpus will actually slow down and earn less points because the benchmark 3850 will do better.
2. The ATI client still has a lot of optimization to do. I have a HD 4870, its ppd has gone from around 3k to about 5k with the newest client and the largest WU. CPU usage has dropped from maxing out a core to using only 25%. Nvidia has already done pretty much all the optimization they can do client wise. (Remember how much they marketed CUDA with folding, they put in a lot more effort than ATI did with folding) Basically this is the idea, the HD 4870 has 800 shader processors, the HD 3870 has only 320. Thats about 2.5k performance if it can all be accessed. So do the math, 4 or 5 times 2.5 is 10-12.5k ppd! Of course this is over optimistic but it obviously shows there is more power in the HD 4870 for folding than is recognized.
3. Theoretically ATI gpus have much greater number crunching power, 1.2 t flops for the 4870, compared to 500-600 g flops for the GTX 260-280.
Thats about it, now all we have to do is wait for new ATI clients to get their job done...
Since you OCF boys seem to be "in-the-know", are these statements truthful? Are ATI GPUs that highly underutilized with the current client (Only 320 of my 800 shaders being use)?!
Honestly, this would explain the tiny increase in PPD going from my 2900XT to a 4870. If anything that is proof that something is unoptimized right now in the ATI client.
Okay about ATI Vs. Nvidia.
For low end cards, get Nvidia, they definitely out do anything that is currently offered by ATI, mainly because they aren't much improvement compared to the 3850 which is used for benchmarking, and thus sit around the 1.5k ppd area.
However, if you did have the money, it might be best to think twice about choosing Nvidia over ATI. Sure the GTX 260 gets 7-9k ppd, and the HD 4870 only gets 4-5k, but its important to understand how points are assigned.
The benchmark machine is a Radeon HD 3850, points are determined so that no matter what WU the 3850 does, it will get 1.5k ppd per day. For instance all those 511 point WU's the 3850 will do three per day or so. Pretty basic, yes?
Now, Nvidia does well because the current range of WU's are in-efficient on ATI gpus. All gpu work units are very small at the moment, (You know how when you select WU size, you have the option of small, medium, or large? There only are small WU's and a few medium ones out yet) this is due to the GPU client still being early days. So Nvidia cards are essentially optimized for this kind of WU, they have a smaller amount of fast shaders. This is compounded by the fact that the ATI client has huge in-efficiencies so that it can't use any more shaders than were on the HD 3870.
So where am I going with this.
1. Once larger WUs are released, ATI gpus will do much better as they are more suited to this with the greater amount of shaders. Nvidia gpus will actually slow down and earn less points because the benchmark 3850 will do better.
2. The ATI client still has a lot of optimization to do. I have a HD 4870, its ppd has gone from around 3k to about 5k with the newest client and the largest WU. CPU usage has dropped from maxing out a core to using only 25%. Nvidia has already done pretty much all the optimization they can do client wise. (Remember how much they marketed CUDA with folding, they put in a lot more effort than ATI did with folding) Basically this is the idea, the HD 4870 has 800 shader processors, the HD 3870 has only 320. Thats about 2.5k performance if it can all be accessed. So do the math, 4 or 5 times 2.5 is 10-12.5k ppd! Of course this is over optimistic but it obviously shows there is more power in the HD 4870 for folding than is recognized.
3. Theoretically ATI gpus have much greater number crunching power, 1.2 t flops for the 4870, compared to 500-600 g flops for the GTX 260-280.
Thats about it, now all we have to do is wait for new ATI clients to get their job done...
Since you OCF boys seem to be "in-the-know", are these statements truthful? Are ATI GPUs that highly underutilized with the current client (Only 320 of my 800 shaders being use)?!
Honestly, this would explain the tiny increase in PPD going from my 2900XT to a 4870. If anything that is proof that something is unoptimized right now in the ATI client.