MS11-LD (M7891-DA)

Don North ak6dn at
Sun Feb 5 21:14:51 CST 2006

Wai-Sun Chia wrote:
> Quick one:
> Can I plug a M7891-DA into a 11/44?
> This is supposed to be 128kW MOS RAM for the 11/24 and 11/34A...
> BTW, what kinds of memory options/expansions does a 11/44 have?
I believe the M7891 (MS11-Lx) is compatible with the 11/44 memory slots, 
but it needs to have some jumpers changed to allow this:

1) Change from MODIFIED UNIBUS (MUD, 18b) to EXTENDED UNIBUS (EUB, 22b) 
   Jumper W4:  MOD/IN  EUB/OUT

2) Change from +15V supply (MUD slot) to +12V supply (EUB slot, 11/44 
   Jumpers W1&W2:  +15v/W1-OUT,W2-IN  +12v/W1-IN,W2-OUT

The MS11-Lx is a parity module, up to 256KB density. More standard 
memory options for the 11/44 would be MS11-Mx 256KB ECC, and MS11-Px 
1024KB ECC.


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