I recently came across a whole stack of old 1U business class servers. They all have dual 3.6-3.8 Xeons (Irwindales) and are surprisingly EM64T with HT for 4 procs total. These are very nice old systems that businesses are practically throwing away lately.
Unfortunately they only have the old PCI-X 100/133, low profile, expansion bays and so finding video cards to stick in these have proven very difficult. My question is, has anyone found a good source of cheap GPUs that will fit these old servers and if so which makes/models?
Option#2: I see PCI-X to PCI-E adapters DO exist, but I can only assume that running a modern PCI-E x16 video card across this bus will ruin the computation potential right?

I recently came across a whole stack of old 1U business class servers. They all have dual 3.6-3.8 Xeons (Irwindales) and are surprisingly EM64T with HT for 4 procs total. These are very nice old systems that businesses are practically throwing away lately.
Unfortunately they only have the old PCI-X 100/133, low profile, expansion bays and so finding video cards to stick in these have proven very difficult. My question is, has anyone found a good source of cheap GPUs that will fit these old servers and if so which makes/models?
Option#2: I see PCI-X to PCI-E adapters DO exist, but I can only assume that running a modern PCI-E x16 video card across this bus will ruin the computation potential right?

Are the PCI-X slots on a riser card?
I have some Dell PE2850 servers at work, dual socket P4's, that came with either PCI-X or PCIe riser cards. So I either get 3 PCI-X 133 slots or 1 PCI-X 133, 1 PCIe x8, & 1 PCIe x4 in a x8 slot.
Something like that might be an option for you. In not the GT430 PCI card might be your best bet.SETI@home classic workunits: 93,865 CPU time: 863,447 hours
Join the BP6/VP6 User Group today!

I agree with HAL9000.
I have a dual Prestonia Xeon, with HT, I run under 32 bit XP Pro (CPUs don't support EM64T. I upgraded the 450W PSU to 650W to run it's works and 2 x GeForce 9500GT in the PCI-X and PCI (not express) expansion slots. The GT430 Fermi will work there as well.It's good to be back amongst friends and colleagues

PCI-X stands for PCI-eXtended so any PCI card should work in them, the extra length basically just adds more bandwidth.
Cheers.

I recently came across a whole stack of old 1U business class servers. They all have dual 3.6-3.8 Xeons (Irwindales) and are surprisingly EM64T with HT for 4 procs total. These are very nice old systems that businesses are practically throwing away lately.
Unfortunately they only have the old PCI-X 100/133, low profile, expansion bays and so finding video cards to stick in these have proven very difficult. My question is, has anyone found a good source of cheap GPUs that will fit these old servers and if so which makes/models?
Option#2: I see PCI-X to PCI-E adapters DO exist, but I can only assume that running a modern PCI-E x16 video card across this bus will ruin the computation potential right?

No it doesn't. See my PCI to PCIE Adaptor and Other Interesting Gizmos thread, and check the computer running the adapter. It's times are almost equal to the card in the x16 PCIE slot.
T.A.

TA is correct. While the PCI bus is not as fast, the actual data transfer across the bus is not a major part of the time taken. Data is send to the card, the card chews on it for a while, and it gets send back. Only the data transfer part of the time is going to be slower, and that's what, 5 or 10% of the total time? Even if that part takes 2 X longer, it's only going to add 10% to the overall task time.
So while you might notice the slightly lower performance, it's not a deal breaker.
If you look from the other side, your old machine will be doing 9X the work it was, instead of 10X if it had a full PCI-E bus.
Might be interesting making it all fit in a 1U chassis? But there are single slot slimline PCI-E cards available that should fit.
That approach makes more sense to me than buying a PCI capable CUDA card. They do exist, but they are not common, or cheap, or very powerful. The PCI-E card is current tech and can be moved to a more modern machine in the future and made to work at 100% in there.
One things that was suggested is they the CUDA processing is likely to load up the PCI bus pretty heavily, and slow down other tasks on the machine, but if it's a dedicated cruncher, or you suspend GPU work while in use this isn't an issue either.
Ian