View source for MMV11-A QBUS core memory

[[Image:MMV11-A.jpg|350px|thumb|right|MMV11-A board set]]

'''MMV11-A''' is a [[core memory|core]] [[main memory]] module for the [[QBUS]] - the only core main memory from [[Digital Equipment Corporation|DEC]] for the QBUS.

An MMV11-A holds 8K [[byte]]s; it has an [[access time]] of 425 nsec, and a [[cycle time]] of 1.15 μsec.

An MMV11-A was composed of two [[DEC card form factor‎|quad-sized]] boards, one piggy-backed on the other, and the pair taking only a single [[backplane]] slot (electrically):

* An H223 [[daughter-board]] containing the cores
* A G653 mother-board containing most of the electronics, and the contact fingers for plugging into the [[backplane]].

The MMV11-A did not use a custom backplane; it plugged into a standard [[QBUS#Backplane|Q/Q backplane]]. However, it did use QBUS signals on the [[DEC edge connector contact identification|right-hand C/D connectors]], so it could not be plugged into a [[QBUS#Backplane|Q/CD backplane]]. 

The pair was 'thick' enough that a normal board cannot be plugged into the next slot. DEC documentation indicates that if there are devices 'behind' the MMV11-A on the bus, the [[bus grant line]]s (BIAK and BDMG) must be [[jumper]]ed on the backplane in that slot.

The MMV11-A was a [[QBUS#Variable_address_size|Q16]] card, so could only be used on systems with a maximum of 64KB of memory.

==See also==

* [[QBUS memories]]

[[Category: QBUS Memories]]