[SI-LIST] PCI/PCIX minimum lenghts?
- From: "Anders Frederiksen" <af@xxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 10 Nov 2005 12:21:26 +0100 (CET)
Hi people =),
I'm working on a board with a PCI-X (66Mhz) and a PCI (33Mhz) bus. Both busses
are
point to point embedded busses. According to specs the minimum length of a PCI
bus
seems to be ~95mm. Given the number of signals and the fact that the optimal
length
is ~3cm I understand the PCB designers frustrations! Thus I'd like to relax the
minimum length constraint...
Has anyone looked into "short PCI busses"? I see two possible issues: 1. Bus
being
too short for transmission line theory to apply. Possibly affecting signal
levels.
2. Timing for host reads: The data will arrive earlier than "expected" due to
the
shorter clock (out) and data (return) propagation.
My googling provided no usable results. Perhaps you guys would have a hint or
two?
Cheers,
Anders
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