MS11-L MOS memory

The MS11-L was final UNIBUS main memory from DEC; a single card can hold enough MOS DRAM chips to fill the entire UNIBUS address space. It had a jumper option to enable use on an Extended UNIBUS. Configuration is by DIP switches. It used parity for error detection.

Fully populated with 16Kx1 chips, it is known as the MS11-LD, and holds 256K bytes. The quarter-, half- and three-quarter-populated versions are the MS11-LA, -LB and -LC, respectively; with 64KB, 128KB and 192KB. All versions include on-board parity support.

It plugs into a MUD backplane (only; not SPC). It is a single hex card, the M7891, so it cannot go in the end slots of the backplane.

The access time is 385 nsec (typical; 1025 nsec maximum on refresh conflict), and the cycle time is 510 nsec (1050 nsec maximum on refresh conflict). Refresh time is 570 nsec (typical; 610 nsec maximum); the time for a complete refresh pass is 14.5 μsec (typical), 13.5 μsec (minimum).

It can use either +/-15V or +/-12V to power the memory chips (in some MUD slots, the 15V pins provide 12V). The board has provision to use battery backup power to retain data during a power outage.