On 07/09/2016 13:02, Noel Chiappa wrote: As does the MicroPDP-11 Systems Maintenance Manual, the Micro-PDP-11 Handbook, some Micronotes, the MICRO/PDP-11 Technical Manual, the IPB, ... Unless DEC sold something like a PDP-11/73S in a BA11-S chassis (like a PDP-11/23plus), it was only used for OEM systems and customer-fitted upgrades. Don't forget the LTC :-) All in all it saves a decent amount of backplane space, makes field service easier, and follows DEC's attempts to integrate as much as possible. Otherwise, you'd need an additional bootstrap card such as an MRV11-D with -B2 boot ROMs, a DLVE1 (DLV11-JE) for the SLUs, something with an LTC, and termination. That's at least twice as many slots in a Q-Q backplane and four slots in Q-CD. A BDV11 wouldn't work as it doesn't have the ROM capability (well, one of mine does but it's been seriously modified, well beyond the ECO for 22-bit :-)). OK, you could use an MXV11-B with -B2 boot ROMs, but that's an expensive way unless you just want a very small (and slower) system, and you might still need termination. And don't forget that DEC sold the microPDP-11/73 as a lower-cost alternative to the microPDP-11/83 which didn't appear until slightly later, or looking at it another way, as a fancier and faster microPDP-11/23. The very first boards had some ASIC/J-11 problems that meant they wouldn't work with an FPJ11, and the first J-11 CPUs wouldn't run nearly as fast as intended so they were fitted with 15MHz crystals (as-sold-by-DEC 11/83 systems have 18MHz crystals). I couldn't possibly imply they were finding a way to sell the inferior parts. After that it's probably all marketing differentiation. -- Pete Pete Turnbull