Atomic investigates NVIDIA’s long-ignored accusation: Is ATI using FP16 demotion to artificially inflate benchmark scores?
The graphics processing world is ever-turbulent. Arguments appear cyclical in nature from both ATI and NVIDIA, and bickering over issues like physics engines isn't uncommon - bringing about phrases like: 'They've been cheating with their so-and-so', or 'We offer the better solution without a drawback like theirs!' from both sides.
It's all part and parcel of competition. However, when Atomic received the recent NVIDIA GTS450 card, press release and included reviewer's guide, we noticed that it came with a page that implied certain unfavourable things about their competition, ATI.
We discovered that this page had been included in every reviewer's guide sent to hardware reviewers since the launch of the GF100 'Fermi' family: the GTX480, GTX470, GTX465, and both GTX460 cards. It had been included with the GTS450 and five other cards, but it seems no-one has paid it much attention, dismissing it offhandedly - as we admittedly dismiss most guides that attempt to dictate our testing methodology.
This page, as it appears below, claims many things. Prime among these is an assertion that ATI were utilising a technique in their drivers called 'FP16 Demotion' to boost their graphical performance at the cost of image quality. It names a number of older gaming titles as the only ones affected by this so-called hack, and welcomes reviewers to work it out for themselves. So, that's what we did.
NVIDIA GTS450 Reviewer's Guide
Important note if you are testing the following applications:
- Dawn of War 2
- Empire Total War
- Need for Speed: Shift
- Serious Sam II
- Far Cry 1
AMD has admitted that performance optimizations in their driver alters image quality in the above applications. The specific change involves demoting FP16 render targets to R11G11B10 render targets which are half the size and less accurate. The image quality change is subtle, but it alters the workload for benchmarking purposes. The correct way to benchmark these applications is to disable Catalyst AI in AMD's control panel. Please contact your local AMD PR representative if you have any doubts on the above issue.
NVIDIA's official driver optimization's policy is to never introduce a performance optimization via .exe detection that alters the application's image quality, however subtle the difference. This is also the policy of FutureMark regarding legitimate driver optimizations.
NOTE: If you wish to test with Need for Speed: Shift or Dawn of War 2, we have enabled support for FP16 demotion - similar to AMD - in R260 drivers for these games. By default, FP16 demotion is off, but it can be toggled on/off with the AMDDemotionHack_OFF.exe and AMDDemotionHack_ON.exe files which can be found on the Press FTP.
For apples-to-apples comparisons with our hardware versus AMD, we ask that you run the AMDDemotionHack_ON.exe when performing your graphics testing with these games. In our own internal testing, speedups of up to 12% can be seen with our hardware with FP16 demotion enabled.
Now, there wouldn't be much point in purely showing performance results without explaining exactly what NVIDIA has accused ATI of: FP16 Demotion. We take a look on the very next page.