Tim: fewer than 21 variations of the M7551, ranging from 1 to 4 >>MBytes of memory. Generally, the -A suffix indicates 1 Mbytes, >>the -B indicates 2 Mbytes, and the -C indicates 4 Mbytes. The >>next letter in the suffix indicates the source of the DRAM chips. At least I'm not crazy (in spite of what people may say!) about the RAM size. My M7551 carries the "CF" suffix. Is there a way that I could get a copy of your module list?? The one that I have from the VAX forum on CompuServe seems to leave out key information. It would be helpful to me for when I go shopping at Temple U. in October. Here's the revised configuration (I actually coppied the numbers down this time). Slot TOP BOTTOM function 8 open open 7 M7512 open buss extender 6 M8639-YA {same} RQDX1 disk controller 5 M9047 M7504 continuity / Ethernet 4 M3104 {same} serial EIA mux-8 3 M7551-CF {same} memory 2 M7135 {same} processor 1 1 M7136 {same} processor 2 Slot 1 is the first slot on the right facing the bulkhead. The buss extender is used to connect to an external RD52 hard drive. Thanks again. ------------------------------------------------- Rich Cini/WUGNET <rcini(a)msn.com> - ClubWin Charter Member (6) - MCP Windows 95/Netowrking