LSI-11/2 CPU with tracks cut?
sb at thebackend.de
Tue Apr 4 03:36:26 CDT 2006
I got a M7270 CPU module here from my PDP-11/03. It has the tracks to
the QBus contacs BC1-BF1 (BDAL18, BDAL19, BDAL20, BDAL21) cut.
I of course wondered why one would do that. In  I found the following
II. Restricted Compatibility Options
Options in this category do not meet one or both of the requirements for
use in a 22-bit system. These options are incompatible with some or all
KD11-HA M7270 LSI-11/2 CPU
(16-bit addressing only, and use of BC1,BD1,
BE1,BF1 for purposes other than BDAL18-21)
So I guess someone tried to make the CPU compatible with 18/22-bit modules?
What did the M7270 use these pins for? I didn't find any manuals or
schematics for the this CPU yet, only for the LSI-11. Could someone
point me into the right direction?
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