20 old servers

[worldinacoin]

I have about 20 servers 2U P4 2 GB Ram 80 GB hard disk, problem is that all of them have only PCI.  But there is an existing rack and datacenter so electricity costs are sunk costs.  Problem is how to upgrade the 20 machines to start mining as efficiency and cheaply as possible.  Any suggestions?

[ovidiusoft]

On these systems you can probably only do CPU mining... without much success. As for upgrading, you'll probably be interested in getting the best GPU / U density. If you can afford it, Supermicro has nice systems that can host 2 double-size/full-length gfx cards in 1U: http://www.supermicro.com/gpu/ .

However, do the math. The hardware is going to be *really* expensive and it's going to be a reaaaaaaaaaaaaaaaaaaaaly long time until you will recover the invested money (if ever). I was in the same situation as you and I dropped the idea in favor of CPU mining (otoh, I don't have old P4s).

[Cosbycoin]

Sounds like you would need to at least change the powersupply and motherboard out to at least accomodate several pci-e 16 slots.

[worldinacoin]

I just need some cheap refurnished graphic cards, maybe it is worth it.  Just that looking for such cards arent that easy.