View source for MS11-L MOS memory

[[Image:MS11-L.jpg|300px|thumb|right|MS11-L board]]

The '''MS11-L''' was final [[UNIBUS]] [[main memory]] from [[Digital Equipment Corporation|DEC]]; a single card can hold enough [[Metal Oxide Semiconductor|MOS]] [[Dynamic RAM|DRAM]] [[integrated circuit|chips]] to fill the entire UNIBUS [[address space]]. It had a [[jumper]] option to enable use on an [[Extended UNIBUS]]. Configuration is by [[Dual Inline Package|DIP]] switches. It used on-board [[parity]] for error detection.

Fully populated with 16Kx1 chips, it is known as the '''MS11-LD''', and holds 256K [[byte]]s. The quarter-, half- and three-quarter-populated versions are the '''MS11-LA''', '''-LB''' and '''-LC''', respectively; with 64KB, 128KB and 192KB.

It plugs into a [[Modified UNIBUS Device|MUD]] [[backplane]] (''only''; not [[Small Peripheral Controller|SPC]]). It is a single [[DEC card form factor|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 [[memory 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, e.g. in the [[BA11-A mounting box]], the '15V' pins provide 12V). The board has provision to use battery backup power to retain data during a power outage. Power requirements are 1.5-1.8A of +5V, 1-1.3A of +5VBB, 9-20mA of -12/-15V (depending on size, i.e. number of MOS memory chips), and 485-700 mA of +12/+15 (when active; depending on size).

==External links==

* [http://bitsavers.org/pdf/dec/pdp11/memory/EK-MS11L-UG-001.pdf MS11-L MOS memory user's guide] (EK-MS11L-UG-001)
* [http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/EK-MS11L-TM-001%20MS11-L%20MOS%20Memory%20Technical%20Manual.pdf MS11-L MOS memory technical manual] (EK-MS11L-TM-001)
* [http://bitsavers.org/pdf/dec/pdp11/memory/MP00672_MS11L_engDrw.pdf MS11-L Field Maintenance Print Set] (MP00672)

[[Category: UNIBUS Memories]]
[[Category: EUB Memories]]