MS11 32KB MOS memory

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The MS11-E, MS11-F, MS11-H and MS11-J are the different configurations of DEC's first commodity MOS UNIBUS memory card, the M7847. They plug into a MUD backplane (only; not SPC).

Fully populated with 4Kx1 DRAM chips, it is known as the MS11-J, and holds 32K bytes. The quarter-, half- and three-quarter-populated versions are the MS11-E, -F and -H, respectively; with 8KB, 16KB and 24KB. (The '-G' is almost certainly not part of the sequence since 'G' is not in the DEC alphabet.)

There are parity versions of each; the MS11-EP, -FP, -HP and -JP; to have the parity operate, these require an M7850 parity controller in the same backplane as the memory card. The M7847 is a hex card, so it cannot go in the end slots of the backplane.

The access time is 550 nsec (1250 nsec maximum on refresh conflict), and the cycle time is 700 nsec (1400 nsec maximum on refresh conflict). Refresh cycle time is 25 μsec (typical), 22.5 μsec (minimum).

The board has provision to use battery backup power to retain data during a power outage. Configuation is by DIP switches; the first DEC memory to do so.