4.3BSD Quasijarus

On Sat, Dec 27, 2008 at 8:29 PM, Steven M Jones <classiccmp at crash.com> wrote: Yeah... that would be a great question to have answered... from what I recall from 20 years ago, there's 5 slots in a KA730 backplane wired to work with memory, but only enough to refresh 5MB of 1MB cards. You could stuff two 4MB cards in a late-model 11/750 with a newer memory controller (plus six 1MB cards), but the 11/750 could *not* be expanded more because it's VAX address space was limited to 24 bits of RAM out of 32 bits total (16MB total address space, like an MC68000). I haven't closely examined the KA730, but *if* one could fill the entire address space below 8MB with RAM, one could theoreticaly make a new-build 8MB single card for it, perhaps with a fresh address line run to a memory slot. I would be surprised to hear that one could exceed 1MB/slot in an unmodified KK730 backplane. These days, I'd personally recommend sets-of-four SRAMs to make a 32-bit-wide datapath, making 2MB trivial to put one one card, *if* the memory slots would easily support that. I've run wires on a 256K-card VAX/11-750 backplane. I don't mind finding a way to support 8MB in one to four cards on an 11-730Z backplane, even if it necessitates fresh backplane wires to pass along extra multiplexed address bits. Encoders and decoders are plenty cheap compared to limited backplane realestate. -ethan