PCI CLK Trace Length

The spec actually is silent about motherboards (well, it specifies round trip times), but if you are designing an add-in card, the spec (as I recall it - it's at home) is that CLK is required to be 2.5 +/-

0.1 inch. That's for PCI (R2.2) and PCIX (up to 133) 1.0a

If you are attempting to design a PCI device, I strongly suggest you get the spec and read it. Don't say you don't have the time - you'll be extremely lucky to get a PCI system working if you don't at least read the physical layer spec.

Cheers

PeteS

Absolutely! For a more readable text on PCI (or PCI-E) MindShare

has some excellent books and eBooks. They're not a substitute for the spec but will help understaning the spec.

--
  Keith

Yes i already have that book. But then i see some PCI clk trace w/c are 'tromboned'...

Yin