PCI-64: how to find

Velocet math at velocet.ca
Mon Feb 25 15:05:25 EST 2002


On Mon, Feb 25, 2002 at 02:11:03PM -0500, Patrick Geoffray's all...
> Velocet wrote:
> 
> > 6.5us for Myrinet vs 32/33 pci being 8? Doesnt seem like the win that
> > it usually seems to be spec'd at. Are these #s accurate? ('out of the blue'
> > warning notwithstanding ;)
> 
> Euh, yes, I think they are: 6.5 us with a 64/66 PCI, 8 us with a 32/33 
> PCI (Lanai9 at 200 MHz). The main difference here is the PCI clock, the 
> latency with a 64/33 MHz is between 7.5 and 8 us.

with what size packets? Wouldnt the latency reduce for a several hundred
byte packet just because the bus is that much wider? and twice the effect
for 66/64 pci? Is the cost of 64 gigabit cards vs 32 worth it for things
sensitive to latency?

/kc

> 
> Patrick
> 
> ----------------------------------------------------------
> |   Patrick Geoffray, Ph.D.      patrick at myri.com
> |   Myricom, Inc.                http://www.myri.com
> |   Cell:  865-389-8852          685 Emory Valley Rd (B)
> |   Phone: 865-425-0978          Oak Ridge, TN 37830
> ----------------------------------------------------------
> 

-- 
Ken Chase, math at velocet.ca  *  Velocet Communications Inc.  *  Toronto, CANADA 
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