Subtle PCI weirdness

gregory.menke at gregory.menke at
Thu Apr 24 18:49:59 UTC 2003

Chris Caudle writes:
 > > The 3com docs indicate the board only does 4 byte dma- 
 > > though the card is a 64 bit unit, its plugged 
 > > into the backplane via a 32 bit connector. 
 > Check REQ64#, ACK64#, and the byte enable signals (C/BE# 4-7) to
 > see if either the card or bridge is getting confused about whether
 > the transactions are 64 bit or 32 bit.  It almost sounds like one
 > of the bridges is getting confused about how to translate between
 > 32 bit and 64 bit devices.
 > -- Chris Caudle

I suspect something like that because the connectors we're using are
something of a kludge- the person who procured these boards didn't
specify cpci, so we got PCI cards instead- then someone ELSE ordered a
set of pci card to cpci connector adaptors (these are 32 bits), which
themselves are connected onto a 64 bit capable cpci extender board.
Its all rather horrific looking but works well enough to talk to the

I'm switching over to a mtx603 which has a 64 bit pci slot and will
continue working there.


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