Intel 860 PCI bandwidth problem
maurice at harddata.com
Fri Jan 18 21:40:37 PST 2002
In recent test on motherboards with Intel 860 chipsets we were seeing less
than wonderful transfer rates using Wulfkit and Myrinet cards.
After some explorations on kernel issues, and other hardware forums we were
still not seeing any reason why this was happening.
Recently Intel published updated chipset errata lists, and I scanned over them.
One issue quickly popped out at me, and I now know what the problem seems
In the file found at:
Intel lists errata for the 860 chipset.
One of these states:
"5. Sustained PCI Bandwidth Problem:
During a memory read multiple operation, a PCI master will read more than
one complete cache line from memory. In this situation, the MCH pre-fetches
information from memory to provide optimal performance. However, the MCH
cannot provide information to the PCI master fast enough. Therefore, the
ICH2 terminates the read cycle early to free up the PCI bus for other PCI
masters to claim.
Implication: The early termination limits the maximum bandwidth to ~90 MB/s.
Status: Intel has no fix planned for this erratum."
This effectively eliminates the 860 chipset motherboards from contention
for HPTC clustering use, IMHO.
Any thoughts from anyone on this?
With our best regards,
Maurice W. Hilarius Telephone: 01-780-456-9771
Hard Data Ltd. FAX: 01-780-456-9772
11060 - 166 Avenue mailto:maurice at harddata.com
Edmonton, AB, Canada http://www.harddata.com/
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