Looking for ancient ram

I have an old compaq server in my basement that has 1.5 gigs of ram in it. I know it supports up to 8 gigs, but I'm having trouble finding what kind of ram it takes, and I'm sure I'll have even more trouble finding the ram should I ever need some more.

It's a compaq proliant 6000. it's dimensions are ~ 3'x3'x3', if that helps at all. Any help to get me started in the right direction would be helpful.

Compaq Proliant EDO ECC DIMM kit
Search for EDO ECC DIMM on ebay you will find what u r looking for or google.

Thanks a bunch

you can also check what CPUz's memory tab pulls up info wise on the computer (to give you an idea wich speed so you don't HAVE to get HP branded if you don't want to)