[hinnersd]

Has anyone ever tried to populate the other pads on a GE 16-4?  There are pads for 4 additional Geometry Engine chips.    

[Raion]

Considering the rarity and possibility of damage, no. It hasn't crossed my mind. Plus I would need to cannibalize it off another board.

[hinnersd]

Well, the 16-4 was used in IR2, 3 and 4 so there seems to be more of those around than say RM11's.   And if someone has a couple dead ones...

[Raion]

My concern would be power draw, shorts, and potential damage. We don't know if those sockets are even hooked in correctly or what. And it's likely that the ROMs on board don't even know how to detect them.

If we had a skilled electronics expert dissect the boards and disassemble the ROMs and tell us that yeah it's not going to hurt anything and you can actually make it work I think it would be a worthwhile endeavor but until that day comes is anyone really wanting to sacrifice a perfectly working board for such an experiment? I think not.

[vishnu]

The geometry engine chips are socketed but soldering in their VLSI surface mount chips would be a nearly impossible job to do by hand.

[Irinikus]

I've always wondered why they never came out with a GE 16-8, even though the GE board was clearly designed to hold 8 GE's! As geometry performance is IR4's weak point!

I wonder if it can't be done professionally?

[jan-jaap]

Rumor has it SGI did this for a big US defense contractor.

The number of GE chips on the board is probably configured somewhere, either with components on the board or in flash somewhere. Without documentation you will never figure it out. BGA replacement is specialist work, so expensive, and if you have a company do this for you they will not guarantee a successful outcome. Now multiply by four for a GE16-8 ....