Recent AMD760MPX chipset PCI measurements??

[Greg Lindahl]

On Thu, Feb 07, 2002 at 07:56:52PM -0700, Paul Lu wrote:

> In late November/December, there was some exciting news about the
> (then) forthcoming AMD 760 MPX chipset and the Tyan S2466 motherboard,
> especially wrt 64-bit/66 MHz PCI performance with Myrinet.

That was me.

> To quote:
> 
> 	DMA rate for 4096 Byte transfers (64bit / 66MHz bus)
> 	1st: 8 pages from bogus sdma pg, 8 to bogus rdma
> 	        bus_read  (send) = 315 MBytes/s
> 	        bus_write (recv) = 341 MBytes/s
> 
> 
> which is a bit disappointing.

Why?

Actual Myrinet transfer rates are generally about 10% slower than the
raw PCI transfer rate, which is the number reported above. What this
is saying is that this PCI implementation is capable of running a
Myrinet link at full speed. Sure, it would be great if it was as fast
as the fastest Serverworks Pentium III chipset, but the only benefit
would be slightly less overhead within the chipset.

-- greg