RE: Motherboard questions

[Lame Brooks-G14738 <brooks.lame@motorola.com>]

If I recall correctly, output drivers meeting the PCI spec are supposed to
be able to drive 10 typical loads.  The approximation of one PCI connector =
one load is based on the characteristics of the typical PCI connector/card
combination.  And of course, the design guidlines in the PCI spec are
deliberately conservative in an effort to increase reliability and relieve
implementers of some significant simulation work.  Designing a reliable
system beyond the PCI Spec's guidlines is possible if you are careful about
what your changes impact.  When you violate spec guidelines, it is always a
good idea (often considered mandatory) to check the validity of your work
with simulations.
-- BrooksL

> For instance if a bridge can drive 6 loads, 
> using the spec I calculate that it can only drive 3 physical 
> connectors (since one connector is considered a load) is this 
> true??  I find that interesting since I have seen other 
> products that use similar bridges to drive 6 physical 
> connectors?!?!  Since these products exist are there ways to 
> route the PCI signals on a motherboard such that a bridge can 
> drive the full of  loads??  Is this limitation due to the PCI 
> signals and the clock or just the clock??  
> Thanks for any help, 
> J 
> W. J. Gomes III 
> Hardware Engineer 
> ComputerBoards, Inc. 
> 16 Commerce Blvd. 
> Middleboro, MA 02346 
> Voice: (508) 946-5100 x279 
> Fax: (508) 946-9500 
> email:walter.gomes@computerboards.com 
>