View source for MS750 Memory System

[[File:VAX-11750_Backplane.JPG|300px|thumb|right|/750 backplane from behind, showing the slots occupied by the MS750 in the centre]]

The '''MS750 Memory System''' is the [[main memory]] for the [[VAX-11/750]]; it consists of:

* one Memory Controller module (MCM)
* one to eight memory array modules

The Memory Controller Module connects to the /750's [[CPU/Memory Interconnect]] [[bus]], and also to an internal memory bus - which does not seem to have a formal name - which runs to the memory array modules' slots.

The Memory Controller Module (either L0011, L0016, or L0022) resides in a custom slot in the main [[backplane]]; slot 10. The memory array modules have their own slots in a dedicated section of the backplane, 8 slots in total. (The physical backplane itself, [[DEC part number]] 50-13821/70-16486, is shared with the [[Central Processing Unit|CPU]]).

A later version, the '''MS750-HB''' which used the then-new L0022 Memory Controller Module, allowed the use of up to two M7199 4MB memory array modules; the older Memory Controller Modules were restricted to smaller memory array modules.
 
==MS750 Memory Controllers==

[[Image:256KBMemoryArray.jpg|thumb|200px|right|256KB module]]

There were three different Memory Controller Modules for the MS750:

* L0011 - up to eight [[M8728]] 256KB memory array modules = 2MB max.
* L0016 - up to eight [[M8750]] 1MB memory array modules = 8MB max.
* L0022 - up to two [[M7199]] 4MB memory array modules and six M8750 1MB memory array modules = 14MB max.

(14MB of Memory is the architectural limit of the VAX-11/750)

[[Image:1MBMemoryArray.jpg|thumb|200px|left|1MB module]]
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The earlier array modules are also used with the [[MK11 memory system]] of the [[PDP-11/70]].

==Further reading==

* ''MS750-HB User Guide'' (EK-MS75H-UG-001) - not online (yet; coming soon, we hope)
* ''MS750-HB Field Maintenance Print Set'' (MP-02061) - not online

==External links==

* [http://www.bitsavers.org/pdf/dec/vax/750/EK-MS750-TD-001_VAX-11_750_Memory_System_Technical_Description_198009.pdf VAX-11/750 Memory System Technical Description] (EK-MS750-TD-001) <!-- https://www.vaxhaven.com/images/9/97/EK-MS750-TD-001.pdf -->
* [https://vt100.net/mirror/hcps/si75fin1.pdf VAX-11/750 Installation Manual] (EK-SI75F-IN-001) - the MS750 is covered in Chapter 9 (pp. 131-132 of the PDF)
* [http://www.bitsavers.org/pdf/dec/vax/750/MP01404_750_Engineering_Drawings_Memory_Controller_198206.pdf Comet Memory Unit Field Maintenance Print Set] (MP01404) - covers the L0016
* [https://manx-docs.org/collections/hcps/m8750.pdf M8750 Field Maintenance Print Set] (MP01398) - very faint scans
* [http://www.bitsavers.org/pdf/dec/vax/730/MP01270_11-730_Engineering_Drawings_198204.pdf 11/730-Z Field Maintenance Print Set (MP01270)] - the M8750 is covered in MS730-C Field Maintenance Print Set (MP01366) (pp. 292-12 of the PDF)
* [https://web.archive.org/web/20071004184324/http://computer-refuge.org/compcollect/dec/vax/11750/L0016-big.jpg L0016 (MCM)] - Memory Control image

[[Category: VAX Memories]]
[[Category: CMI]]