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Re: S-100 Motherboard

I had a suspicion about what was causing the 6502 (DOS/65) problem
with the 5.25 inch drives and a quick check confirmed the cause. I had
created a memory conflict with the monitor RAM used by the low level I/
O routines called by the OS and the SIM (same as CBIOS) host buffer
that only manifested itself with drives using 512 byte sectors, i. e.,
the 5.25 inch drives. The 8 inch SSSD drives use 128 byte sectors and
the hard disk uses 256 byte sectors which is why they both worked

I just had to do a new SYSGEN with a 256 byte longer space allocated
to SIM and the conflict was eliminated. That was pretty simple and was
accomplished in a few minutes.


Both CP/M and DOS/65 are working well with the seven drives - I am
declaring victory and the next step is to move the motherboard and
power supplies into the old cabinet after ripping out the old
motherboard and the many pound linear supply. I will hold onto that
linear supply as many of the components are the same as in the eight
inch drive power supply so I'll have some spares.


PS: The eight inch A drive that was relegated to read only status now
appears to be writing at least some of the time. I accidently saved a
file to A: that I was transferring into the system using XMODEM from
my development laptop. It wrote the file to the A: drive without
error. I don't want to make a habit of doing that as a flaky write
could screw up the directory. Go figure...