memory assignment jumpers MM8EJ

Mike Katz bitwiz at
Sat Nov 6 15:00:20 CDT 2021

This should help:

On the G104 board there are some jumpers EMA0, EMA1 and EMA2.  These 
correspond to the the bits of the extended address of the board.
A jumper inserted means 0 and a jumper removed means a 1.

EMA    0     1      2
   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

Please note that the MM89EJ is an 8K memory board and will take up two 
memory fields, the one selected and the one selected plus 1 (i.e.  if 
the jumpers are in out in, the memory will be on fields (EMA) 2 and 3).

This information can be found on page 2-6 of the PDP-8/e PDP8/f & 
pdp-8/m Processor Maintenance Manual Volume 1:


On 11/6/2021 1:47 PM, Bill Degnan via cctalk wrote:
> I am unable to confirm for sure the memory assignment process for I know
> without a doubt how to set their page assignments.  I can guess but that's
> dangerous and inefficient.  I want to test an unknown core stack, so I need
> to know which RAM space I am testing.
> I have a PDP 8e core stack with the following:
> H121 8x12 core
> G233E
> G111C
> Anyone know the process of assigning the RAM space on the boards?
> Bill

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