I'd say the system is worth $50, especially if you get to pick and choose the best parts from three of them. It's reputed to be an excellent retro gaming system due to a good onboard sound setup and some flexible slowdown features... there's at least a couple threads about it here if you do a search. A couple notes, though:

The ram looks funny- it's EDO but not 30 or 72 pin SIMMs.

They're 3.3v unbuffered ECC EDO DIMMs, I believe. They're quite a bitch to find, so if you buy the machine, make sure you load it up with as much memory as you can... you're probably not going to run across any more for quite awhile.

motherboard cache ram

Uh, there shouldn't be cache on a PPro board... it's built into the CPU.

Does this system need a boot floppy to install Windows from a CD?

Depends whether the Windows CD is bootable. The machine can boot from a CDROM drive, if that's what you're asking.

As for installing a hard drive, if you use a newer drive... I wanna say 30GB or larger... you should make sure to first upgrade to BIOS A10. Older versions of the BIOS had problems with newer hard drives and would throw a completely unhelpful 'Hard Disk controller failure' error on boot.

Thanks Old Trashbarg, just the answers I was looking for!

Old Thrashbarg basically said it all! 😁

The PPro's alone can be worth a big chunk of the $50 the seller is asking for it. The 3.3v EDO DIMM's seem harder to find, I only got like 1 or 2 32MB ones or so (no idea how I got them 🤣).
I'd say, fill up ALL of the memory slots and maybe ask him if you can take a couple spare parts, in case the motherboard is dead?....a bit of a longshot but might as well ask. He might go along with it if you throw in some of your own dead hardware as part of the bargain?

I've bought it! Look up the retro rig photo thread... thanks for the advice dudes!