From: B Degnan (billdeg_at_degnanco.com)
Date: 2009-03-08 23:38:51
To anyone who cares about the B Series 8088 Co-processor..
I have strong circumstantial evidence that the program space used by the
original CBM 8088 co-processor (intended for but not officially sold for
the B Series) conflicts with the space that the CBM 256-80 BASIC ROMS
use, and therefore a stock CBM 256-80 will not work with the 8088
co-processor. That explains why the 2 256's with the co-processors I
have came with B128 BASIC ROMS in them. I will bet that no one with a
8088 co-processor and 256 BASIC ROMS will be able to get it to work
properly. By swapping ROMS with another working system and/or working
parts I learned of this situation. Only when I had the following ROMS in
a hi-profile B Series system would the co-processor work:
901243-02 (B128 BASIC)
901242-02 (B128 BASIC)
901244-03 (probably not important KERNAL)
Both the HIBOY PLA 906114-05 and 906114-04 work with the 8088 co-proc.
To reiterate - "common knowledge" is incorrect, it's not the PLA that
makes a hi-profile board compatible with the 8088 co-processor, it's
probably the BASIC ROMS (you can't use the stock CBM 256-80 ROMs).
I would need to dump the program listing of the 8088 co-processor to
confirm this. If there is a strong interest I will attempt to pull it
down, time permitting. This is one of those things I will do
eventually, and when complete I will share with this group.
Bill Degnan
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