Suggestions for VT103?

Jerome H. Fine jhfinedp3k at
Sun Dec 28 07:15:24 CST 2008

 >Glen Slick wrote:

>>On Sat, Dec 27, 2008 at 6:41 PM, Jerome H. Fine <jhfinedp3k at> wrote:
>>Using an M8190 quad 11/73 board is probably your best choice with as much
>>memory as possible.
>You wouldn't really want to put an M8190 KDJ11-B in a VT103 Q-Q
>backplane instead of a Q-C/D would you?
Jerome Fine replies:

Not a problem.  The M8190 will operate in both ABAB and ABCD backplanes.
I have successfully used an M8190 (a quad board) with a 4 MB memory board
(also a quad board)  in a VT103 backplane that had been upgraded to 22 bits.
Note that since the VT103 backplane is ABAB on all 4 slots, it is not 
to use PMI memory as PMI memory.  The PMI memory can, of course, be used
as ordinary memory.

I have heard that it is possible to alter the first 2 ABAB slots to be 
ABCD so that
PMI memory can be used - or a Micro Vax II can be used.  No details are 

>An M7554 KDJ11-D/S might be more suitable for the Q-Q backplane.
>Address bits 18 - 21 are on BC1 - BF1 (SSPARE4 - SSPARE7)
>BC1 - BDAL18L
>BD1 - BDAL19L
>BE1 - BDAL20L
>BF1 - BDAL21L
A diagram would be helpful to identify the required points on the backplane.

By the way, I stated (incorrectly) that 16 solder points are needed.  
Actually, 32 solder
points are required, 2 for each slot (both AB and AB on each slot) and 4 
slots and
4 address lines for a total of 8 solder points per wire and 4 wires.  
Lead based solder
is needed for this very old backplane.

Sincerely yours,

Jerome Fine

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