Sounds like you might need to add 3.3 volts to your pci slots

There are a variety of projects and solutions you can search for on this forum to solve.

Re: Adding 3.3v to pci

Remember also you have a version of the earliest type of pci

Good luck

Thank you, this could be it. Is this a general problem with AT motherboards? As far as I understand, AT power supplies do not have a 3.3V rail at all. So the only solution would be to build a device that generates 3.3V from 5 or 12V and then solder that to the board or card? Since I have no knowledge about electronics, this wouldn't be possible. But at least it's good to know why it won't work.

I've just had a look at the PCI pin specifications: https://pinouts.ru/Slots/PCI.shtml

On the old card that works (S3 Virge), the +3.3V pin (number 25) leads nowhere, but on the Riva, it goes into the graphics chip.

asdf53 wrote on 2022-07-09, 13:43:

Thank you, this could be it. Is this a general problem with AT motherboards? As far as I understand, AT power supplies do not have a 3.3V rail at all. So the only solution would be to build a device that generates 3.3V from 5 or 12V and then solder that to the board or card? Since I have no knowledge about electronics, this wouldn't be possible. But at least it's good to know why it won't work.

A general problem with incorrectly keyed PCI cards. There's a key you're supposed to use if the card requires 3.3V, but 9 times out of 10, manufacturers used the regular 5V keying, even on cards like this that need 3.3V. The board is doing exactly what its spec and its slots imply, it's the card that should be warning you that it won't work - but doesn't.

Note that there certainly exist nVidia PCI cards that will work with 5V only.

dionb wrote on 2022-07-09, 17:28:

asdf53 wrote on 2022-07-09, 13:43:

Thank you, this could be it. Is this a general problem with AT motherboards? As far as I understand, AT power supplies do not have a 3.3V rail at all. So the only solution would be to build a device that generates 3.3V from 5 or 12V and then solder that to the board or card? Since I have no knowledge about electronics, this wouldn't be possible. But at least it's good to know why it won't work.

A general problem with incorrectly keyed PCI cards. There's a key you're supposed to use if the card requires 3.3V, but 9 times out of 10, manufacturers used the regular 5V keying, even on cards like this that need 3.3V. The board is doing exactly what its spec and its slots imply, it's the card that should be warning you that it won't work - but doesn't.

Note that there certainly exist nVidia PCI cards that will work with 5V only.

I did some digging and from what I understand, the signalling voltage of the card is independent from its internal operating voltage - a card could use 5V for signalling, but still require 3.3V for one of its chips to operate, and the keying system doesn't account for that: https://www.ics.uci.edu/~harris/ics216/pci/PCI_22.pdf (Page 113). Apparently, the whole 3.3V thing was introduced with PCI 2.0 in 1993, and the board came out in 1993 or 1994 - so maybe it's still a PCI 1.0 board?

My TNT2 card has a regular 5V notch and the Riva 128 has both 5V and 3V notches. But this doesn't seem to give any clue whether the card requires 3.3V to operate.

asdf53 wrote on 2022-07-09, 20:19:

[...]

I did some digging and from what I understand, the signalling voltage of the card is independent from its internal operating voltage - a card could use 5V for signalling, but still require 3.3V for one of its chips to operate, and the keying system doesn't account for that: https://www.ics.uci.edu/~harris/ics216/pci/PCI_22.pdf (Page 113). Apparently, the whole 3.3V thing was introduced with PCI 2.0 in 1993, and the board came out in 1993 or 1994 - so maybe it's still a PCI 1.0 board?

3.3V wasn't compulsory until PCI 2.2, so as a rule, 2.0 and 2.1 boards did not implement it. This board has SiS 501 chipset whch IIRC supports PCI 2.0.

That's good to know, thanks! It's hard to find any information on this except for that PCI 2.2 specification sheet.

Edit: I've just tried the cards in another old board (FIC 486-VIP-IO, Socket 3). This one specifically mentions in the manual that it is PCI 2.0, and the cards also didn't work there.

I was really excited when I found out that there are some Riva128 and TNT PCI cards that do not require 3.3V. The ELSA Synergy II PCI (Riva TNT2) is one such card, it has none of the 3.3V PCI pins connected, and it has an onboard voltage regulator that takes 5V and outputs 3.3V, so I assume it is generating its own 3.3V power without relying on PCI.

I was finally able to get one of these cards, and when I tested it in my Socket 4 and Socket 3 boards - nothing. No picture, the PC is not booting (no hard drive noise), and the chip gets barely warm. An ampere meter shows that it's only drawing about 2 watts, so it's clearly not doing anything. What a bummer! The card works fine in my Socket 7 boards.

There must be something else going on. I had a look at the PCI 2.1 specification, if I understood correctly there is a 5A power budget for the 5V PCI rail, but that is shared between all slots, there is no guaranteed minimum power per slot. So it's either that, or something else that makes it operate out of specification. I am now looking for a Riva 128 that is 5V only, though after all that, I'm not very optimistic that it would work.