MM11-Y core memory
The MM11-Y was a 64 Kbyte core main memory for PDP-11 UNIBUS machines. It provided parity, so its formal name was MM11-YP.
An MM11-Y was composed of two hex boards, one piggy-backed on the other, and the pair taking only a single backplane slot (electrically):
- An H228-B daughter-board containing the cores
- A G657 mother-board containing most of the electronics, and the contact fingers for plugging into a backplane
The MM11-Y did not use a custom backplane; it plugged into a standard MUD slot. The pair was 'thick' enough that a normal board cannot be plugged into the next slot; instead, a G727 grant continuity card must be used there (since it has no components on it, it just clears the H228-B card).
The core array provided two more bits per word, to support byte parity; parity operation used an M7850 parity controller plugged into the same backplane as the MM11-D.
It is possible to interleave a pair of MM11-Y's to provide reduced effective average access times.
Further reading
- MM11-YP User's Manual (EK-MM1YP-UG) - not available online
- MM11-YP Technical Manual (EK-MM1YP-TM-001) - not available online, exists in fiche
