Chipsets and memory speed...

Greg Lindahl glindahl at
Sun Dec 10 14:08:49 PST 2000

> I am looking for a chip set (motherboard) that can easily handle 2 PCI
> cards streaming 50-60MB/sec each. One is moving data from the main
> memory and the other is putting data into main memory.

It depends. Your problem may be that the OS overhead of processing all the
calls is too much for the CPU to handle.

Myrinet, which is a pretty low-OS-overhead network, is capable of hitting
100 MB/s on lots of motherboards.

It can be tricky to figure out what the OS overhead is independent of the
chipset costs of PCI DMA and the like.

> I believe the L440GX doesn't allow both CPUs
> to access main memory at the same time.

ALL current Intel motherboards have a single shared bus for all CPU access
to main memory. PCI DMA to main memory may or may not collide with CPU to
main memory transfers.

In your case, is it possible to have the cards transfer directly to each
other? That's an interesting trick you can do with Myrinet: you can send
from a disk controller to Myrinet or from Myrinet to a video card without
going through main memory.

-- g

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