MS11-K MOS memory
The MS11-K MOS memory modules were the first generation of memory array modules used in the MK11 memory system for the PDP-11/70. (The functional difference between the 256KB version of the MS11-K, and the later M8728, is currently unknown.)
Each MS11-K module was a hex board, the M7984. Fully populated, the board holds a total of 156 DRAM chips, including 28 to hold the ECC. According to the prints, it could be used with 4Kx1 chips, giving 64KB total storage; or 16Kx1, giving 256KB.
Per the prints, these are the configurations and board types:
| Board | Model | Size | Configuration |
|---|---|---|---|
| M7984-Ax | MS11-KA | 64KB | 156 x 4K chips |
| M7984-Bx | MS11-KB | 32KB | 78 x 4K chips |
| M7984-Cx | MS11-KC | 256KB | 156 x 16K chips |
| M7984-Dx | MS11-KD | 64KB | 39 x 16K chips |
| M7984-Ex | MS11-KE | 64KB | 156 x 4K chips |
| M7984-Fx | MS11-KF | 128KB | 78 x 16K chips |
(The 'x' in the board number is one of a number of letters, starting with 'A', which indicates the manufacturer of the DRAM chips used.)
It is not confirmed exactly what the difference is between the -KA and the -KE; the prints show the latter as a replacement for the former, and describe the latter's RAM chips as "fast RAM" (200nsec versus 75nsec).
