MM8-E Memory System - Revision history

Jnc: Thinko (-EJ is clearly after -EH; matching datea on prints

2023-05-11T13:57:04Z

Thinko (-EJ is clearly after -EH; matching datea on prints

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	The '''MM8-E Memory System''' was the standard [[main memory]] system on [[DEC]] [[PDP-8/E]]; it was [[core memory]]. The MM8-E was the first [[PDP-8 family]] core memory system to use the [[core memory#Technical details\|shared sense/inhibit line]] technical innovation. The initial '''MM8-E''' version was 4K [[word]]s; a later 4KW variant was the '''MM8-EH'''. That ~~had been preceded~~ by an 8KW-sized variant, the '''MM8-EJ'''.		The '''MM8-E Memory System''' was the standard [[main memory]] system on [[DEC]] [[PDP-8/E]]; it was [[core memory]]. The MM8-E was the first [[PDP-8 family]] core memory system to use the [[core memory#Technical details\|shared sense/inhibit line]] technical innovation. The initial '''MM8-E''' version was 4K [[word]]s; a later 4KW variant was the '''MM8-EH'''. That was augmented by an 8KW-sized variant, the '''MM8-EJ'''.

	==Implementation==		==Implementation==

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2022-05-27T19:06:42Z

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	* [https://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8ej.pdf MM8-EH & MM8-EH - 3]		* [https://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8ej.pdf MM8-EH & MM8-EH - 3]

	[[Category: PDP-8 ~~memories~~]]		[[Category: PDP-8 Memories]]

Jnc: Fairly complete

2021-11-07T20:53:30Z

Fairly complete

New page

The '''MM8-E Memory System''' was the standard [[main memory]] system on [[DEC]] [[PDP-8/E]]; it was [[core memory]]. The MM8-E was the first [[PDP-8 family]] core memory system to use the [[core memory#Technical details|shared sense/inhibit line]] technical innovation. The initial '''MM8-E''' version was 4K [[word]]s; a later 4KW variant was the '''MM8-EH'''. That had been preceded by an 8KW-sized variant, the '''MM8-EJ'''.

==Implementation==

All versions consisted of sets of three [[DEC card form factor|quad]] boards:

* X-Y Driver and Current Source G227/G234 (4K); G233 (8K)
* Sense/Inhibit G104/G115 (4K); G111 (8K)
* Memory Stack Assembly H211/H220 (4K); H212 (8K)

The Engineering Drawings indicate that the two X-Y Driver and Sense/Inhibit variants can be mixed in any combination in an 8KW set; for the 4KW set, it calls for the G115-G211 combination.

They were connected with four H851 [[over the back]] Edge Connectors, in two sets of two; the Stack Assembly, in the center, has four groups (often called 'rows' in DEC documentation) of contact fingers on the back edge of the boards, and the other two each have two sets of contact fingers.

==Configuration==

Setting the [[PDP-8 Memory Extension units|field]] of the MM8-E is done with three [[jumper]]s on the G104/G111/G115 Sense/Inhibit board: EMA0, EMA1 and EMA2 (which set the bits of the ''starting'' field in the extended [[address]] of the MM8-E). Since a field is 4KW long, an 8KW set will use two fields: the one selected as the starting field, and the one above that one.

{| class="wikitable"
! EMA !! EMA0 !! EMA1 !! EMA2
|-
| 0 || In || In || In
|-
| 1 || In || In || Out
|-
| 2 || In || Out || In
|-
| 3 || In || Out || Out
|-
| 4 || Out || In || In
|-
| 5 || Out || In || Out
|-
| 6 || Out || Out || In
|-
| 7 || Out || Out || Out
|}

A jumper is inserted for a '0', and removed for a '1'.

==External links==

* [http://www.bitsavers.org/pdf/dec/pdp8/pdp8e/DEC-8E-HMM1A-D-D_PDP-8e_Maintenance_Manual_Volume_1_Processor_Sep73.pdf PDP-8/E, PDP-8/F & PDP-8/M Maintenance Manual Volume 1] (DEC-8E-HMM1A-D-D) - covers the MM8-E on pp. 95-126
* [http://www.bitsavers.org/pdf/dec/pdp8/pdp8e/MM8-EJ_Engineering_Drawings_May73.pdf MM8-EJ Engineering Drawings]
* [https://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8e.pdf MM8-EH & MM8-EH - 1]
* [https://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8e-b.pdf MM8-EH & MM8-EH - 2]
* [https://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8ej.pdf MM8-EH & MM8-EH - 3]

[[Category: PDP-8 memories]]