There's also a little bit about the MS11-C (not covered in the documents above) in EK-11045-MM-007. There is a later rev of the MS11 manuals, which does cover the MS11-C; Chuck McManis had both of them: EK-MS11A-MM-006 MS11-A,B,C memory systems maintenance manual EK-MS11A-OP-001 MS11-A,B,C memory systems users's manual but when I contacted him about them a while back, he wasn't sure if he still had them, or if he'd given them to Al K to scan and put up (he was on the road at the time, so couldn't check if he still had them). Al, are they in your queue somewhere? (No rush to do them, if so; I just want to make sure we know where they are.) Studying the MS11 Maint Manual, the MS11 controller has access to the full address and data from both the CPU (FastBus) and UNIBUS B. (The FastBus actually has two uni-directional data busses; in and out.) So all that info, this hypothetical cache board can get from the slot it is plugged into (assuming the cache is plugged into one of the controller slots), over its connector pins. The connectors on the back of the card, and two small boards, must be for listening to UNIBUS A (in configurations in which the two UNIBI aren't joined together)? (I'm too lazy to check the slot numbers are see what they actually are.) And there is indeed a signal which the MS11 uses to tell the CPU it has the location the CPU is asking for, so it's theoretically possible to build a cache card that plugs into a FastBus slot. Noel