Problem with DEC LSI11 / KD11-F

Pete Turnbull pete at
Sat Nov 29 15:00:40 CST 2014

On 29/11/2014 20:22, Mattis Lind wrote:
> I have been browsing through some of my old Qbus boards and found one
> KD11-F (M7264) CPU with 4 k word memory, a couple of KD11-HA (M7270) , a
> KDF11-A (M8186) and some assorted memory boards and some SLUs.
> All CPUs seemed to work except for the KD11-F board

> The M7264 board has the following chips:
> CP1611B-51  2111549
> CP1621B451  23001C201
> CP1631B-10   23088A501
> CP1631B-07   23087A501
> The M7270 board has the following chips:
> 1611H  21-15579
> 3007D  23-002B5
> 3010D   23-001B5
> 2007C   23-002C4

As far as I knew, they used the same chipset with the same instruction 
set, but those are clearly different.  The 21-15579 is the ALU etc, the 
23-xxxxxx are the microcode ROMs.  Obviously you could swap the 
21-15579, but you probably can't mix-and-match the ROMs.  It couldn't be 
that one set is something other than a PDP-11 instruction set?


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