On Mon, 22 Jun 1998, Mark A. Corio wrote:

> Hi all,
> I am working on a project with multiple PICs doing various things. They end up
> reporting to a board that is installed in a PC on the PCI bus (for other
> reasons). Does anyone know the voltage levels on the expansion PCI slots in a
> PC? My impression is that it is 5V, unlike the North-side PCI bus (next to the
> processor) which is 3.3V. Any help or pointers is appreciated.

Hi Mark,

I had to design a PCI bridge a couple of years ago, so I'm a little rusty,
but the PCI connector tells all. In the slot there are plastic keys, and
the PCI cards themselves have slotted cutouts to prevent them from being
inserted in a slot with the wrong voltage. The card  I designed was meant
for 5 volts only, so I didn't have to deal with dual-voltage busses at
that part of the circuit. look at a couple of PCI cards and the connectors
in a computer and you'll see what I mean.

Sorry I can't be of more help, it's been a while,  perhaps others are more
fresh on the subject.

Cheers,
bob