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Microbenchmarking Intel’s Arc A770
- timw4mail 4y agoI'm kind of disappointed all the tests were without ReBAR. I'm curious as to what kind of difference that makes.
- onli 4y agoYou are probably aware, but ReBAR has a huge effect on these card, so much that it is a requirement to get stable and acceptable FPS in games. I would assume that means the effect would be huge also in those smaller benchmarks. edit: But was it really off in general, or only for the PCI-e 3.0 part of the article?
- wtallis 4y agoReBAR only matters for transfers across the PCIe link, so for most of the tests in the article it's completely irrelevant. And even for the PCIe transfer tests, ReBAR should only affect the portions of the tests that are accessing more GPU memory than the default BAR size used for 32-bit compatibility.
- timw4mail 4y agoConsidering how much the Arc series loves to share system memory, I'm not so sure.
- wtallis 4y agoIntel's having to find and fix every place their drivers assumed that the CPU's RAM and the GPU's RAM were the same pool of memory. As a result, it's completely unsurprising that they're struggling with performance in real applications and games, but it doesn't provide a reason to expect microbenchmarks such as these to run afoul of an irrelevant problem.
- TomVDB 4y agoIt would make zero difference, except, maybe, for the PCIe bandwidth test. Because all other tests were stressed interfaces that reside within the GPU silicon itself or between the GPU and the DRAM. Even the numbers of PCIe bandwidth test might not change much, even it's trying to test medium size memory to memory block transfers.
- clamchowder 4y agoApologies for the confusion, the tests were run with ReBAR. I've updated the article to reflect that Shouldn't affect the conclusion for anything besides the PCIe copy to/from GPU tests.
- ErneX 4y agoThese GPUs practically require ReBAR, performance without it drops significantly.
- DRAGONERO 4y agoIs the benchmark suite available somewhere?
- clamchowder 4y ago(Author here) See https://github.com/clamchowder/Microbenchmarks/tree/master/GpuMemLatency https://github.com/clamchowder/Microbenchmarks/tree/master/G... It's very much a work in progress, as noted in the article. And some of the stuff that worked reasonably well on my cards, like the instruction rate test when trying to measure throughput across the entire card, went down the drain when run on Arc.
- jra101 4y agoHave you tried reducing the register count in your FP32 FMA test by increasing the iteration count and reducing the number of values computed per loop? Instead of computing 8 independent values, compute one with 8x more iterations: for (int i = 0; i < count * 8; i++) { v0 += acc * v0; } That plus inlining the iteration count so the compiler can unroll the loop might help get closer to SOL.
- clamchowder 4y agoThe problem is loop overhead matters on AMD, because AMD's compiler doesn't unroll the loop. Nvidia's does, so it doesn't matter for them.
- WithinReason 4y agounroll with #pragma unroll?
- atlgator 4y agoI would love to get my hands on one. They seem to be sold out everywhere.
- MegaDeKay 4y agoIf on Windows, you might want to check out the Gamers Nexus reviews on YouTube: the Intel drivers are a dumpster fire and build quality is... not great. https://www.youtube.com/c/GamersNexus/videos https://www.youtube.com/c/GamersNexus/videos