I had probably the same problem on my Supermicro P3TDLE when I installed my Parhelia 512 pci and Win2k. I'm not sure what fixed it but my brain wants to say it was when I set MPS 1.4 Support [Disabled] is when it started working.

I'm not sure if that was it because a bit later I set MPS 1.4 Support [Enabled] and yet it continued to work.

Your Supermicro board looks like exact same layout as the asus from me.

I tryed serval bios setting on the PCI side, with and without MPS 1.4 support. But nothing changed.

Siv show me its a NTP bridge from PLX. Looks like win2k is loading the wrong driver for it.
Did back than special ServerWorks Driver exists for PCI-X and so ?

I didnt use any special Serverworks driver. I think changing the MPS setting in bios didnt work with an existing install and I had to set it to MPS1.1 and do a new install of Win2k to get it to set the correct resources for the bridge chip on the Parhelia.

tryed reinstall as you say with mps support off. I have no option for 1.1. But no luck.
So two PCI bus systems, one for the 32bit slots and one for the 64bit. But the bridges dont connect.

Well it was a few years ago so not really sure how I got it to work exactly, I normally need to know what is wrong and how I fixed it but with that problem I just took the win and as soon as it was working I made an image of the drive.

Maybe we were having slightly different problems. My Parhelia 512 pci (Parhelia PCI-X 256 MB) was still working while I was having the problem it was the Matrox drivers were not recognizing the card specially the bridge part of it. It kept giving the problem that it couldnt give resources to the bridge part of it so I looked into the Matrox cards and their Bus mastering. I found a link or two of others back in the day having the same problem but no answers were given.

I cant remember what other things I tried I know during one of my multiple re-installs of Win 2k it just worked, I tried fiddling with the changes I thought I made to get it to go back to the same problem but after that it always just worked.

Maybe others Re: A useless short analysis on PCIX to PCIe bridge performance on Tualatin

ok i got it working!
I had the joy doing multi installs of win2k.
For me it worked with :

Bios settings:
VGA Snoop : enable
PCI Latency : 64
MPS 1.4 : disable

Than Win2k F5 installed as Multi MPS. After that the ressource are all found correctly and anything working.
Thanks for the help!

Glad you got it working I know it drove me nuts trying to figure mine out. I'm going to write down what you did for future reference in case I have problems.