Unknown slot in some Macs?

[IIsi]

I noticed that in some Macs, there is a long slot behind the last NUBUS slot. It is visible in a IIx (but not a II) a IIvx, and the IIci. Now I know that in a IIci, it should be the slot for the cache card, which checks out, given that I have seen these installed in IIci's. However, evidently this ONLY works in a IIci nothing else. But I checked out the signal traces, and these slots (On a IIvx anyway) are missing 3 signals relating to cache, so they can't be cache card slots. I have seen a photo online of a IIvx with this slot populated. Any ideas what this is for? Some kind of accelerator slot perhaps?

Here is the shot of the IIvx without the card (looks like a IIci cache card slot, doesn't it?)

http://www.gateman.com/ebay/mac.iivx.....jpg

Here is a shot of a IIcx with the slot populated! Wtf???

http://www.gateman.com/ebay/mac.iicx.........jpg

**Edit: The developer docs for the Ivx mention that it is basically an accelerator card, and is the same as the IIci cache card minus the cache control signals, preserving the rest of the pins that an 030 PDS slot might have. I am thinking this prob answers my question. Although....has anyone ever heard of cards made for these slots?

 

[OtakuMegane]

They're PDS slots and in most cases each model was different. IIci has a cache card that can go in it and quite a few CPU upgrades that were made for it, including a couple 601 PowerPC upgrades. IIcx and IIx should be able to take some CPU upgrades as well. I believe the slots are the same design for those two. I don't know much about the IIvx.

 

[Bunsen]

http://macfaq.org/hardware/cards.shtml#Q2.6.1

 

[sircabulon]

i have a IIcx with a 68LC040 accelerator in it. 25Mhz woo hoo!