11/14/2023 0 Comments Nvidia geforce gtx 970![]() ![]() The GTX 970 does have 4GB of VRAM, and it can use all of it, but accessing those last 500MB will decrease performance. PCPer points out that the last chunk of VRAM is still four times faster than system RAM (your DDR3) accessed via PCIe. What we don’t know, exactly, is how much that actually matters for gaming. If you look at the Nai benchmarks (pictured above) floating around, this is what you are seeing.”Īccessing that last 500MB of VRAM is absolutely slower than accessing the first 3.5GB. PCPer writes: “Let's be blunt here: access to the 0.5GB of memory, on its own and in a vacuum, would occur at 1/7th of the speed of the 3.5GB pool of memory. Few games (currently) require more than 3.5GB of VRAM, so the primary pool can be accessed at maximum bandwidth. ![]() ![]() Nvidia avoided that problem by dividing the memory into a 3.5GB pool and a 0.5GB pool. This would cause dramatic underutilization and would prevent optimal performance and efficiency for the GPU.” So the overall bandwidth would be roughly half of peak. PCPer explains “if the 7th port is fully busy, and is getting twice as many requests as the other port, then the other six must be only half busy, to match with the 2:1 ratio. Because the GTX 970 only has seven ports connecting memory controllers and cache, one of those ports would always be burdened with twice as many requests. If you don’t speak graphics card, PCPer helps break down the architecture of the GTX 970. The SMMs are the bottleneck, not the ROPs.” Before people complain about the ROP count difference as a performance bottleneck, keep in mind that the 13 SMMs in the GTX 970 can only output 52 pixels/clock and the seven segments of 8 ROPs each (56 total) can handle 56 pixels/clock. That means the GTX 970 has 56 ROPs and 1792 KB of L2 cache compared to 64 ROPs and 2048 KB of L2 cache for the GTX 980. NVIDIA says this was an error in the reviewer’s guide and a misunderstanding between the engineering team and the technical PR team on how the architecture itself functioned. First, despite initial reviews and information from NVIDIA, the GTX 970 actually has fewer ROPs and less L2 cache than the GTX 980. "You should take two things away from that simple description. However, the 32-bit memory controller segment remains. With a GTX 970 though, only 7 of those ports are enabled, taking one of the combination L2 cache/ROP units along with it. That interface has 8 total ports to connect to collections of L2 cache and memory controllers, all of which are utilized in a GTX 980. connected to the SMMs through a crossbar interface. “The most important part here is the memory system. On Sunday, Nvidia Senior VP of GPU Engineering Jonah Alben spoke to PC Perspective about the issue, and we finally have clarification on where that discrepancy comes from. These numbers look bad, though we can’t vouch for the veracity of data provided by the benchmark. This user-created Nai’s Benchmark claims to show that the memory bandwidth of the GTX 970 drops dramatically when accessing that last 500MB, while the same problem does not affect the GTX 980. Those are also average framerates, which don’t address the problem some commenters have pointed out: dramatic framerate stutter at the moment the GTX 970 starts utilizing its final 500MB of VRAM. Nvidia’s point is that the GTX 970 behaves just like the 980, with performance only decreasing about 1-3%, comparatively. It’s hard to analyze the effect of pushing either card past 3.5GB of VRAM with the numbers provided above the framerate will naturally be lowered by running a game at higher resolution or AA settings. As you can see, there is very little change in the performance of the GTX 970 relative to GTX 980 on these games when it is using the 0.5GB segment.” On CoD: AW, the drop is 41% on GTX 980 and 44% on GTX 970, a 3% difference. On Battlefield 4, the drop is 47% on GTX 980 and 50% on GTX 970, a 3% difference. On GTX 980, Shadows of Mordor drops about 24% on GTX 980 and 25% on GTX 970, a 1% difference. >3.5GB setting = 3840x2160 FSMAA T2x, Supersampling on ![]()
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