ION platform Bandwidth ? Get only 5 to 6 GB/s for deviceToDevice MemCpy

Hi all !

I can’t figure out what is the theoritical maximum bandwitdh of ION LE platform ?
I ran the bandwidth test included in the CUDA sdk 3.0 and got results between 5 to 6 Gb/s for a device to device MemCopy.

Do you have any explanations ?

Thks !


ION doesn’t have any dedicated video memory, so I guess that is the bandwidth of host ram you have in the system.

5-6GB/sec. looks right to me if the ION has a 128-bit DDR2 interface (just like the 9400m chipset).

64 bits of DDR2 memory @ 800 MHz = 6.4GB/sec. 1000MHz = 8GB/sec, and 667MHz DDR2 = 5.2GB/sec.

But the memcopy will read at that speed and then write at that speed so dividing that peak bandwidth speed by two is a good estimate… and multiply it by two for each multiple of 64-bit bus width.

Edit: If your ION is using DDR3 then that alters the calculation as well (see the link).

AFAIK Ion and the 9300M/9400M chipset are one and the same thing (technically MCP79a is the chipset name). Ion LE is also the same chipset, just with one MP fused off. The only major difference between any of the MCP79a versions is the gpu core clocks and the addition of DDR3 support in some cases.