@thomasfuchs Hey there! I decided to give it a go myself again today, and this is my result!

* standard PC (i440fx)
* 486 CPU / 256MB of RAM
* cirrus VGA
* pcnet nic (auto detected during setup)

This all worked out of the box for me! If it won't for you I suspect some local firewall settings on your machine.

@thomasfuchs - does the switch still support 10Mbit ethernet or is it set up as 100/1000 only?

@thomasfuchs My personal experience is that current QEMU has a ton of bugs, where ATA doesn‘t work as expected, Cirrus Graphics produces glitches … so I‘d suspect a buggy emulation here too and try a different NIC.

Regarding NT3.51 I had that part working on an earlier version of QEMU, but chose PCnet as NIC.

@thomasfuchs I don't know the answer exactly, but in PCs IRQ 2 of interrupt controller 1 is wired to IRQ 9 of the second interrupt controller and it's referred to as cascade.

Interrupt 2 and 9 are essentially the same thing. Although even today when working with old PCs I'll avoid using IRQ 2 or 9 for ISA devices because it does 'act weirdly'.

If possible try to move the card to IRQ 7 and disabled the printer port, or IRQ 5 if you don't plan to use a sound card.

@thomasfuchs - sorry, I was recalling my experience with the real thing.

In the QEMU docs and in the UTM docs, other network cards are specifically mentioned and the NE2000 isn't. I include this tidbit only for the general public, since you know how to google and stuff.

@thomasfuchs glad to hear it!

What are you going to do with your new vm!

@hydrian thanks! that's a good lead... I see the driver in the OEM package. I think I can make a ISO image to load into QEMU to install it.

@thomasfuchs Sorry. Nasty headache.

If i'm remebering correctly, NT3.5 and NT4.0 NE2000 drivers were garbage. You always had to go out the extact drivers from the NIC's OEM and couldn't use the generic one. Your best bet using the rtl8139 NIC by qemu. The drivers are at https://www.realtek.com/Download/List?cate_id=587 in the OEM packages.

@thomasfuchs oh, 3.51 has pcnet drivers built in, I was confused with my 3.1 VM...

@thomasfuchs if DHCP works it's probably not the IRQ no, sorry I misread your initial post.

When I last tried to run nt3 in qemu I used the pcnet nic instead of ne2k I don't remember exactly what didn't work with ne2k tho, so I'm hesitant to guarantee that it'll make a difference for you.

But it is a PCI card, so it just might not be suitable for what you're trying to do. Nt driver below!

https://archive.org/download/windows-nt-3.1-files-from-vpsland/pcnet.7z