I just read this review using the 7950 CF vs 660TI SLI. Looks like the 7950 CF won every benchmark. Then I read the conclusion .
It's nothing new that SLI is superior to CF in terms of user experience. With AFR, fps are not telling the whole story. You can read this over and over again in multiple reviews, from multiple user reports. AMD should finally work this out with CF, but I wouldn't hold my breath.
Every bit of "extra smoothness" nVidia has increases input lag in the process
Although the review did show 7950 winning at higher frame rates nothing in the review showed AMD in a light where it needed to be at a certain frame rate. At least no specific game was pointed out causing issue. Also the 7950 is similarly priced or in some cases lower then what it was benched against. So you have 7950's offering higher frame rates and sold at a lower price point.
We've run a number of other benchmarks and need to add, for the sake of fairness, that Nvidia's advantage is only evident if its driver is optimized for smooth frame rates rather than raw performance. The company takes certain apps, like synthetic benchmarks and commonly-tested games, and tweaks them to yield higher numbers at the expense of consistency.
@ Boxleitnerb - this is a year old but good article on both, and it touches on Nvidia's sli optimisations - http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html
I'm actually surprised that I didn't hear a lot more about that.
Overall, SLI had a slight advantage with two cards, but 3-way Crossfire appeared to almost eliminate microstutter completely.
Three-way CrossFire is very compelling in most games and benchmarks. However, driver issues reduce its performance to the level of a dual-GPU setup in a few applications. In those cases, the only remaining benefit of three-way CrossFire is better frame rate consistency in each of the tests we ran (admittedly, no small gain)
AvP -Neither Nvidia nor AMD manage to avoid micro-stuttering in multi-GPU mode. Only the three-way CrossFire setup is more or less OK.
Call of Juarez -It takes a three-way or four-way CrossFire setup to approach the quality of Nvidia's SLI output.
Mafia II -Apart from the three-way and four-way CrossFire setups, which do provide solid performance and low levels of micro-stuttering, AMD's dual-GPU CrossFire implementation isn't impressing us. Nvidia emerges victorious here.
The poor scaling on the 3rd card is more likely explained as...poor scaling on the 3rd card. We've been seeing this from both companies for years. In the Tom's article the 3-way crossfire 6870's consistently score lower fps than the 580 sli (as you would expect), and consistently get noted as having lower microstutter - or it's at least 2 wins and 2 draws.The three-way CrossFire setup is the overall winner if you want to keep stuttering to a minimum.
Every bit of "extra smoothness" nVidia has increases input lag in the process
The Portland Group® (PGI), a wholly-owned subsidiary of STMicroelectronics and the leading independent supplier of compilers and tools for high-performance computing, today announced that PGI Accelerator™ Fortran, C and C++ compilers will soon target the AMD line of accelerated processing units (APUs) as well as the AMD line of discrete GPU (Graphics Processing Unit) accelerators. PGI will work closely with AMD to extend its PGI Accelerator directive-based compilers to generate code directly for AMD GPU accelerators, and to generate heterogeneous x64+GPU executable files that automatically use both the CPU and GPU compute capabilities of AMD APUs.
"The PGI Accelerator compilers will open up programming of AMD APUs and GPUs to the growing number of HPC developers using directives to accelerate science and engineering applications," said Douglas Miles, director, The Portland Group. "Together with AMD, we are working to make heterogeneous programming easily accessible to mainstream C and Fortran developers, and to unleash the power of these devices."
"We look forward to working with PGI to ensure that through the use of standard compiler directives the full computational power of AMD platforms with integrated APUs can be easily tapped," said Terri Hall, Corporate VP, Business Alliances, AMD. "Engagements like this are key to expanding the developer ecosystem and the opportunities for AMD platforms."
I've noticed that it can be induced by changing the tRAS (Active to Precharge Delay) from it's predefined value or Command Rate from 2T to 1T. So it's not just the cpu from what I've experienced.The author confuses cause and effect. Not the reduced microstutter is the cause for reduced performance/scaling. Reduced scaling due to a CPU bottleneck is the cause for less microstutter. I have made some experiments on this by downclocking my CPU significantly which led do massively reduced microstutter in several games.
They didn't show the stutter graphs for each game, however they have commented on them below the fps graphs.
Metro - AvP - Call of Juarez - Mafia II - The poor scaling on the 3rd card is more likely explained as...poor scaling on the 3rd card. We've been seeing this from both companies for years. In the Tom's article the 3-way crossfire 6870's consistently score lower fps than the 580 sli (as you would expect), and consistently get noted as having lower microstutter - or it's at least 2 wins and 2 draws.
Exactly what I thought. If something is CPU limited, the microstutter necessarily disappears (as the GPUs are waiting for the game engine, the updates are evenly distributed over time) or one has a badly programmed engine that produces also stuttering on a single GPU.The author confuses cause and effect. Not the reduced microstutter is the cause for reduced performance/scaling. Reduced scaling due to a CPU bottleneck is the cause for less microstutter.