Later Realtek NICs are notorious for only working if 3.3V is available (despite universal keying) - the RTL8139B was the last one to work on legacy 5V PCI buses.

Can't comment on that specific TNT2-M64. I certainly have had M64s that would run in a 5V-only PCI 2.1 slot, but YMMV.

dionb wrote on 2021-08-29, 19:07:

Later Realtek NICs are notorious for only working if 3.3V is available (despite universal keying) - the RTL8139B was the last one to work on legacy 5V PCI buses.

Bah, if it's that then RIPperoni... At least I managed to source a 3Com adapter that should work.

EDIT: TNT M64 card picks up fine on my Windows 98SE machine

3Com cards are solid bets for PCI 2.1 support. I think early Intel Gb NICs also are (I recall using one in a BX system) although I'm not sure if there are any DOS packet drivers for them, and I'm not happy with the Intel (well, Crynwr - Intel just links to them) E100PKT driver (overflows all over the place with long FTP queues when running FTPSRV). I'm generally not one for going all fanboy on one vendor, but when it comes to DOS, I'm yet to find something as troublefree as 3Com's offerings. Save the nice Intel NICs for OSs that can handle them. And Realtek... they're primitive but get the job done, at least, if they like your PCI slots.

Interesting, did not know many Realteks did not like 5v PCI slots...
The only difference in the PCI slot part of a 3.3/5v card is the 12th pin is cut out to fit the 3.3v pci slot, that 12th pin is one of many grounds so it must be a card + bios issue with that TNT card.
I tested a bunch of pci vid cards in my P/I-P6NP5 AT board a few months ago and 1/2 were 3.3/5v type, everyone of them worked just like a few years before when tested on one of the low end P4 boards.

Consumer motherboards in general are 5V PCI due to location of PCI notch is 5V only. The 3.3V part is used on server boards. I searched for long time and seen this pattern.
Secondly, it is chipset and bios firmware that counts more on ability to initialize the PCI-based video cards. I had seen this before, where not all works with Micronics HX board, but works better with later board like AN430TX for example.

Cheers,

I guess I can attempt to update the bios to the latest available (which I'm apparently not on); worst case I brick it and I have more reason to swap my DOS build over to a 440BX with one of the Via C3s I've on the way, though I'd prefer a working board to hand off to someone else