geforce 1080 vs 1070

[foldy]

GTX 1080 on PCIe gen2 x1 and only 7% performance loss then there is no real pcie bus usage limit on linux. And what about Windows?
@Nathan_P: Did you test on Windows?

[Nathan_P]

No, tested on the zorin 9 distro of Linux with the 352 NVidia driver

[bruce]

Yeah, good point. I guess I'm trusting NVIDIA's software to provide good feedback. I just took it to mean that once the atoms are loaded into the GPU's memory, there isn't a lot of traffic back and forth. I'm probably very, very wrong in that assumption!

Yeah, this makes more sense than the huge bandwidth usage often quoted on windows - I can't believe that it it's really using 2 GB/s continuously (50% of 8x gen2). I'm seeing 1-2 % of gen2 4x on linux for a 980. I suspect that the 'usage' shown in windows might be similar to the cpu usage used by the drivers - it's just polling, not actually doing anything useful most of the time. I'm going to try a 1080 on a gen1 1x riser, and I'm not expecting to see much of a slowdown, but will report back after experimenting.

[bruce]

Yeah, good point. ... I just took it to mean that once the atoms are loaded into the GPU's memory, there isn't a lot of traffic back and forth. I'm probably very, very wrong in that assumption!

The atoms do represent a significant amount of data ... N*M scalar values. where N is the number of atoms and M represents the number of scalar values needed to describe an atom (much smaller than N). There's a lot more data in the force matrix, which is at least 3 times N*N/2 so there's a pretty good chance that the code will continually page it in and out in some fashion.