On Aug 17 2006, 20:31, Scott Quinn wrote: I'm not sure exactly what version that is but it does supply refresh for the memory, although only the very earliest memory boards actually need that -- in fact your MSV11-B is the only one I can think of that does -- and it's sometimes disabled. W4 controls that, it's inserted to *disable* it. And that board possibly has 8K bytes of memory on it already, which needs the refresh enabled. Are the five MICROM sockets right at the edge of the board, or is there some circuitry just to the left of them? The former is KD11-F, the latter is KD11-J. Usually the former has on-board memory, usually the latter does not. If there's a 23-003B5 chip in the leftmost socket, you have the optional KEV11, which contains the EIS/FIS instruction set. You didn't mention -- or I missed it -- what backplane you have. I'm guessing it's a "straight" backplane like an H9273. If so, what the LSI-11 puts on the C/D fingers shouldn't matter, unless you put something immediately below it that dislikes the LSI-11. I don't think there's anything untoward on C/D, though, because they can be used in "serpentine" backplanes like the H9270 used in the small BA11-M box for small 11/03 systems. Interesting; that's a slightly later vintage than the other parts. That will need an RX01 (or an RX02 with the switches set for RX01 emulation) dual 8" floppy drive. This one needs the refresh control signal from the LSI-11. The 18-bit designation for the memory means that it has two parity bits as well as the 16 data bits, and the processor will ignore that. Actually, the MSV11-P has it's own parity CSR so some OSs might be able to use it. It might not work because the extra address lines may not be held at the right level -- the 11/03 only has 16 address lines and no memory management, and it puts some extraneous signals on the top 4 address lines -- but although the MSV11-P supports 22-bit addressing, it also works in 18-bit systems, so it's worth trying and it shouldn't do any harm to try it. If it does work, you'll end up with 56K bytes of usable memory, because the top 8K byte page is reserved for I/O. The 16/18/22-bit designations can be confusing when you're talking about memory, because they normally refer to the size of the address bus and hence the address range. An 11/03 (and any CPU using an LSI11 or 11/02) has only 16-bit addressing. An 11/23 may be 18-bit or 22-bit, later processors are 22-bit. However, 16-bit and 18-bit are sometimes used in the contect of memory to refer to the data bus width: 16 bits with, or without, two parity bits. I wouldn't say so. It's a fairly simple machine, as -11s go. You want to see if you can acquire some of the DEC handbooks for those systems, such as the 1976 "Microcomputer Handbook" and perhaps the 1978-79 "Memories and Peripherals Handbook". Other useful ones are the 1982 "Microcomputers and Memories" handbook (doesn't say quite so much about the LSI-11, though, but it does list the jumpers and etch revisions etc), 1980 "Microcomputer Interfaces Handbook", and 1983-84 "Microcomputer Interfaces Handbook". Plus, of course, you should see if you can get any of the engineering drawings as they too contain a lot of useful information. -- Pete Peter Turnbull Network Manager University of York