Re: S-100 Motherboard

[Rich Leary <richar...@gmail.com>]

Today was a mixed day but basically good.

Before I tried to boot CP/M I tried my 28 (?) year old, wire-wrapped 2
MHz 6502 CPU board. My S-100 system always had the ability to swap CPU
boards between Z-80 and 6502. The 6502 board was key to developing my
OS, DOS/65.

I pulled the Z-80 board and inserted the 6502 and powered up. It came
up and since the monitors are basically the same I was able to do the
same things.

I powered down and hooked up my 8 inch drives and the hard disk.

Both CP/M and DOS/65 drives are configured the same:

A - 8 in SSSD - as configured is always the boot drive
B - 8 in SSSD
C - 5.25 in 40 track DSDD (Kaypro IV)
D - 5.25 in 80 track DSHD (1.2 MB - custom format)
E - CP/M hard disk partition - 3672 blocks of 2048 bytes per block,
256 byte sectors - the first half of the drive
F - DOS/65 hard disk partition - same size as CP/M partition - the
second half of the drive
G - 5.25 in 40 track SSDD (Kaypro II) - same physical drive as C

I powered the system up with the 6502 CPU, inserted an 8 in DOS/65
boot disk and wonder of wonders DOS/65 came up and worked perfectly. I
did not actually hook up the 5.25 in floppy drives so did not test
them yet.

The F drive worked perfectly just as it had when I last used the
system three years ago.

I also re-confirmed that there is a bad sector on drive E and it is in
the directory area of that partition. That  is also consistent with
what I saw last time I brought either CP/M or DOS/65 up. As an aside -
the system has no provision to remap bad tracks and the Xebec S1410
controller will only allow entire tracks to be flagged as bad. You can
not reformat a single sector or flag a single sector as bad - only
full tracks. That is something I will have to work or I will just wait
for the new IDE controller board.

With the success I had it was time to power down and put the CPU-Z in
the system and try to boot CP/M.

No joy! I did not get a head load and that should happen as soon as I
issue the boot command under the monitor.

I did not get a chance to sort out the problem but I suspect it is
associated with one of the alternate bus signals that may conflict
with what I use with the floppy controller. The CPU-Z has provisions
to use almost every possible signal while the 6502 CPU board has much
less in the way of alternate signal use. In my old system some lines
were pulled high or low to maintain everything in a known state. So I
just need to check those bus signals and check how the CPU-Z uses the
lines not normally used by the floppy controller. I am sure it will
prove to be a simple issue and a simple fix.

Rich