[AG-TECH] PCI specs

Andrew Daviel advax at triumf.ca
Wed Apr 2 13:30:32 CST 2003

(I think I'd seen something on this topic before, but can't find it now)

I've been trying to spec  a Linux PiG machine (really an AG node, 
but I want to have direct VRVS ability and that implies a single ip address for
the capture and display).

I've been running into the PCI problem where recent dual-CPU systems don't 
have all 5 volt PCI slots. I have bought Hauppauge Impact capture cards 
with the Conexant 878 chip (was BrookTree), as I've used them before
and they support S-Video plus 3 composite inputs (switchable). So
I've got 3, maybe 4 capture cards, plus probably an SBLive128 that people 
recommend, plus probably Matrox 450PCI + 550AGP (from seeing what drivers 
appear to be solidly supported  for dual-head DVI output), and either 
onboard LAN or PCI LAN.

The problem is that PCI is no longer just "PCI", but a lot of the 
literature particularly for older cards and motherboards assumes it is.
The PCI spec itself you have to buy, but I found a useful site

It seems that PCI cards may use either 5V or 3.3V signalling on the bus.
They may also be 32-bit or 64-bit, 33MHz or 66Mhz, and PCI or PCI-X

PCI 2.2 supports both 5V and 3.3V signalling. So stated 2.2 compliance 
won't tell you the voltage.
PCI 2.3 supports only 3.3V signalling

3.3V signalling devices must have the output voltage clamped between 0V
and 3.3V, which is usually a function of the chip, even if they use 5V
internally. Bt878 for instance has no support for this, but doesn't say so
in so many words because it was designed before 3.3V PCI was prevalent.
Matrox 450 is a 5V card, and so I strongly suspect is the SB Live 128.

3.3V signalling cards may be identified by a notch at pin 12/13, about 
1cm from the connector end of the card. 5V signalling cards may
be identified by a notch at pin 50/51, about 1cm from the other end of
the card on a 32-bit card. Universal cards which can work at either 
signalling level have both notches.
Sometimes a photo may be the only way to check before buying. Google image 
search seems to find things fairly well.

32-bit cards will work in a 64-bit slot.
A 33MHz card will work in a 66MHz slot, but will downgrade all cards to 
In practice, 66MHz slots seem to also be 3.3V signalling

And then there's PCI-X, PCI-Express, Mini-PCI etc. etc.

PCI-X 1.0 defines 66 and 133 bus speeds.
PCI-X 2.0 adds 266 and 533 bus speeds.

PCI devices installed in a PCI-X bus will work, but will downgrade all 
devices on the bus to PCI speed and protocol. PCI-X supports
only 3.3V signalling.

I'm now looking at Tyan Thunder MB which seems to have 5V PCI ...

Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376
security at triumf.ca

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