The Accusation
Just before the RD580 launch on the first of March, ATI came to the media with some claims about NVIDIA’s X16 chipset and how it was much less efficient than ATI’s own competing architecture. It was said that the connection between the two GPUs was in fact much less than the full x16 PCIe speeds that ATI’s chipset had and that this would mean a less than optimal performance scenario for the end user. ATI provided some data from internal testing they had done that indicated NVIDIA’s bandwidth for communication over the NF4 SLI X16 inter-GPU connection was only around 1500 MB/s compared to ATI’s 2500 MB/s.
This data provided by ATI indicated that NVIDIA’s chipset provided much slower data transfer between the two X1900 XTX cards they used for testing. When the HT multiplier was lowered to 2x and 1x, the results were even lower, as we would expect. Since there is no north bridge to south bridge connection needed for transfer between the GPUs on the RD580, ATI’s results remain the same throughout the graph as it has no multipliers to modify.
Also, ATI conjured up that since NVIDIA’s bandwidth numbers were so much lower than theirs, the fact that the MCP is also responsible for the networking, USB, storage and PCI bus, this would actually turn out to be even more of an issue for users. Since the same connection between the south and north bridges had to not only supply data between the two graphics cards bus also storage data, networking, etc then gaming while using these features would be even slower.
Conclusions
What kind of conclusions can we draw from my own testing data here? First, everyone needs to realize that you should never take any company on their word about performance, features, etc as you are likely to get burned eventually.
Back to the technology aspect of it all, we can see that ATI’s claims of bandwidth levels on the NF4 SLI X16 chipset are simply not valid. Our real world testing shown here obviously demonstrates that even with ATI’s cards involved to eliminate chipset/GPU tweaks, the secondary x16 PCIe slot has no noticeable performance deficit compared to the primary x16 PCIe slot.
Even more indicative of invalidity of ATI’s data is the fact that even when we desperately TRIED to make the NF4 X16 secondary GPU slot slower by bogging down the system with almost a full Gigabit of networking data, a maxed out SATA connection and a maxed out USB/Firewire connection, it didn’t work. The secondary GPU slot performed nearly the same as the primary slot with only very small performance differences under 3%.
Final Thoughts
The truth of the matter is that both the NVIDIA NF4 SLI X16 chipset and the ATI XPress 3200 chipset provided enough bandwidth for today’s SLI and CrossFire generations, at the least. ATI’s attempt to promote their RD580 chipset by showing poor performance numbers on inter-GPU communications didn’t add up in our testing.
For the Detailed Review visit : PcPer
Just before the RD580 launch on the first of March, ATI came to the media with some claims about NVIDIA’s X16 chipset and how it was much less efficient than ATI’s own competing architecture. It was said that the connection between the two GPUs was in fact much less than the full x16 PCIe speeds that ATI’s chipset had and that this would mean a less than optimal performance scenario for the end user. ATI provided some data from internal testing they had done that indicated NVIDIA’s bandwidth for communication over the NF4 SLI X16 inter-GPU connection was only around 1500 MB/s compared to ATI’s 2500 MB/s.
This data provided by ATI indicated that NVIDIA’s chipset provided much slower data transfer between the two X1900 XTX cards they used for testing. When the HT multiplier was lowered to 2x and 1x, the results were even lower, as we would expect. Since there is no north bridge to south bridge connection needed for transfer between the GPUs on the RD580, ATI’s results remain the same throughout the graph as it has no multipliers to modify.
Also, ATI conjured up that since NVIDIA’s bandwidth numbers were so much lower than theirs, the fact that the MCP is also responsible for the networking, USB, storage and PCI bus, this would actually turn out to be even more of an issue for users. Since the same connection between the south and north bridges had to not only supply data between the two graphics cards bus also storage data, networking, etc then gaming while using these features would be even slower.
Conclusions
What kind of conclusions can we draw from my own testing data here? First, everyone needs to realize that you should never take any company on their word about performance, features, etc as you are likely to get burned eventually.
Back to the technology aspect of it all, we can see that ATI’s claims of bandwidth levels on the NF4 SLI X16 chipset are simply not valid. Our real world testing shown here obviously demonstrates that even with ATI’s cards involved to eliminate chipset/GPU tweaks, the secondary x16 PCIe slot has no noticeable performance deficit compared to the primary x16 PCIe slot.
Even more indicative of invalidity of ATI’s data is the fact that even when we desperately TRIED to make the NF4 X16 secondary GPU slot slower by bogging down the system with almost a full Gigabit of networking data, a maxed out SATA connection and a maxed out USB/Firewire connection, it didn’t work. The secondary GPU slot performed nearly the same as the primary slot with only very small performance differences under 3%.
Final Thoughts
The truth of the matter is that both the NVIDIA NF4 SLI X16 chipset and the ATI XPress 3200 chipset provided enough bandwidth for today’s SLI and CrossFire generations, at the least. ATI’s attempt to promote their RD580 chipset by showing poor performance numbers on inter-GPU communications didn’t add up in our testing.
For the Detailed Review visit : PcPer