MS11-K MOS memory
The MS11-K MOS memory modules were the memory array modules used in the MK11 memory system for the PDP-11/70.
There were two generations of memory modules for the MK11.
The original memory module was the MS11-K (M7984). According to the prints, it could be used with 4Kx1 DRAMs (giving 64KB with a total of 156 chips, including 28 to hold the ECC), or 16Kx1. 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 nuber of letters, starting with 'A', which indicates the manufacturer of the DRAM chips used.)
The second memory array module is the M8728, which used 156 16Kx1 DRAMs to provide a 246KB module.
A later board, the M8750, used the same PCB as the M8728, but 64Kx1 DRAM chips - the board had jumpers to allow the use of either size chip - to provide a 1MB card.
This board was not supported by the MK11. However, it is possible to use them in an MK11 with slight modifications. Also, it is theorized that with the appropriate jumper setting, they can be made to look like 256 boards.
