Re: PCI Question

["Ingraham, Andrew" <Andrew.Ingraham@compaq.com>]

> Are there any spare pins in the 32 bit version of the PCI bus that can
> reliably be used for a dedicated function between proprietary cards?
 
No.  These would be called "sideband signals," and section 2.3 in the
PCI Specification says:

"No pins are allowed in the PCI connector for sideband signals."

>   If
> there are unused pins, are they typically bussed between card slots?
 
There are some unused pins on the connector that are identified as
"Reserved."  "Reserved" pins can not be used by any device, nor can they
be bussed.

There exist PCI adapters that plug into two adjacent PCI connectors, and
use something like a ribbon cable between the two cards.  This generally
works OK, but be aware that even that arrangement may not work in a
Hot-Plug system where a physical shield between cards might preclude an
inside-the-box connection.

Regards,
Andy