very high bandwidth, low latency manner? (i860)

Don Holmgren djholm at
Fri Apr 12 16:11:41 PDT 2002

Unfortunately the measured performance doesn't match the published
specs.  DMA rates reported by the Myrinet driver on 64/66 cards are
about 315 MB/sec and 225 MB/sec, respectively, for bus writes and reads.  
See the reported measurements on a number of i860-based motherboards at
Greg Lindahl's page,

This has been a sore point for lots of folks wanting to build clusters
with i860-based machines.

Don Holmgren

On Fri, 12 Apr 2002, Michael Stein wrote:

> > bandwidth was highest on IA64 460GX...). I can't imagine that the i860 can
> > actually perform as well as 340MByte/sec since the Hub-Link (between
> > the MCH and the P64H) has a limit of 266MByte/sec (AFAIK) ....
> The data sheet for the i860 shows 3 separate Hub-links A, B and C.
> A is 266 MByte/sec (and typically runs the 33 Mhz 32 bit stuff).
> B and C are 533 MByte/sec each and drive the P64Hs.
> (16 bits * 66 Mhz * 4x data xfers).
> The pdf is about 1.1 MB.

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