PCI Express 2.0 memCpy Performance

I’d like to know how good the PCI Express 2.0 bus accelerates the
performance of the memcpy hostTodevice and deviceToHost.

The theoretical bandwidth is 8 GB/sec so I guess you could expect
to double the performance from a PCI-Express 1.1 bus.

Since I don’t have a PCI-Express 2.0 capable mainboard I couldn’t confirm that.
Maybe somebody already has experience with the actual up- and download speeds.

Does it really double the performance in real life?
I appreciate anybody who can support me with some measurements.
I’d buy a 2.0 capable card plus mainboard if it really doubles the performance.

thank you!

I haven’t tested any PCIe 2.0 based systems yet, but I would bet that few of them hit 2x the speed of PCIe 1.0. I’d bet that for operations working with pinned memory you’ll see a nice speedup, though I expect you’d have to have a very good motherboard to see something close to 8GB/sec, as that’s getting up near the main memory bandwidths provided by many motherboards. Without the use of pinned memory, you probably won’t see anything close to the peak performance, even on a good motherboard. If I were ordering a new CUDA test box with PCIe 2.0 I’d probably go for a 780i based motherboard as they seem to have good internal and PCIe bandwidth from what I read.

Cheers,
John

What CUDA devices support PCIe 2.0?

8800GT and 8800GTS/512 (i.e. G92-based cards).

@tachyon_john

That’s why I’d like to see real performance measurements ;)
My algorithms are in need of good up and download speeds.
I get around 1,9 GB/sec on an P35 Mainboard with GeForce 8800GTX without pinned memory and 3,2GB/sec with pinned memory.
If i could double the performance (3,8 GB/sec so to speak) with PCI Express 2.0 I’d definately invest in a new Mainboard plus 8800 GTS (for now).

My experience has been that with a PCIe 1.1 x16 and a 8800GTX (also PCIe 1.1) all SLI system (i680, memory, 8800GTX) I get near theoretical. With and PICe 2.0 all SLI i780 system, memory and PCIe 2.0 8800GT, I get just a smidge more, no where near the 2x bump I was expecting from PCIe1.1 to PCIe.20.

Which begs the question: why not?? Are the 8800GT boards really just PCIe 1.1?

Can someone from NVIDIA comment?

With PCIe 2.0 hitting 8GiB/s, the speed of the RAM and chipset will become a big player in determining the performance. Some chipsets, even though they have full PCIe 2.0 to the card don’t have a wide enough pipe to fill the full 8 GiB/s.

See this post and a couple after it for benchmarks. http://forums.nvidia.com/index.php?showtop…ndpost&p=319537

The 8800GT is a PCI-E-gen2 card, and will run as such assuming that there aren’t problems elsewhere (OS, motherboard, etc).