It's time to restore the 11/45.

tony duell ard at
Thu Feb 5 09:35:04 CST 2015

>   I've been reading through the 11/45 manuals and it seems these machines
> are far more complex than I had imagined.  Can anyone understand and
> explain the unibus a / unibus b concept?

This is something I ought to figure out sometime too. AFAIK, it is only significant
if you have the special 11/45 memory boards (MOS or bipolar) in the CPU backplane.

For most applications (read : Anything you or I is going to do at the start), you 
jumper the 2 Unibuses together with an M9200 in A/B of slots 26 and 27 of the 
CPU backplane. This M9200 is just a narrower version of the M920, you can 
probably drill out the rivets and remove the handle of an M920 to make one. I think
I did the reverse at one point. 

If you do this, you can have standard Unibus memory boards on the Unibus, but they
don't go in the CPU backplane. I remember modifying a 4 slot backplane to have an MUD
slot (before I had even heard of an MUD slot) and fitting a 3rd party MOS RAM board.
>  Should I eliminate all this fancy bipolar and core memory and just use an
> m7891?  If I did, would it be on the fastbus, unibus a or unibus b and
> would it even matter?

AFAIK, if you do that you have one bus, Unibus, and it works fine. 


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