Re: S-100 Motherboard

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

It has been a busy few days with a 10-12 inch storm on Thursday night
- Friday morning to create a diversion. Here is status:

a. CP/M and DOS/65 are working fine.

b. I found the original Xebec utilities I had modified to set up my
hard disk (CMI 5619). I reformatted the CP/M partition to eliminate
the error in one of the directory sectors. This left the DOS/65
partition intact but did delete all the CP/M files from E:. I had a
backup on 1.2 MB floppies and was able to restore all the files that
were on the backup diskette set. What is fascinating is that the
diskette set had none of the .ASM or .Z80 files nor were they on the
E: drive before I reformatted that partition. I did have copies of the
key source files (i. e., my BIOS, my BOOT, my monitor ROM, hard disk
setup utilities, and three of the four diskette format routines) on my
PC backup. Why there were not more on either disk or diskette set is a
mystery and since the last time the CP/M system was used was 15 years
ago my memory is foggy about what happened. I recall having
accidentally deleted some files but why both .ASM and .Z80 files would
have disappeared in one step is a mystery.

c. I looked hard at what else I had and what I needed and concluded
that the key immediate need was for a high speed MODEM7 variant to
facilitate PC to S-100 transfers under CP/M. I had a binary version of
MODEM798 set for the Interfacer IV but it was only configured for 4800
bps and I wanted to use 19,200 just as my DOS/65 software can do when
the 6502 CPU is installed. I eventually settled on MDM727.ASM as the
SIG/M archives had an overlay for the Interfacer IV. Silly me - I
thought it would be a no brainer to set the parameters in the overlay,
merge the files, and charge ahead. It turned out that the overlay had
several coding errors that manifested themselves as soon as I ran
ASM.COM on the source file. While these errors did not take too long
to fix it is fascinating that the code had been in existence since
1984 with some very obvious errors. The problem was that the errors
were only obvious when changing the default conditional assembly
variables. In the end it was a simple few fixes and MDM727 is now
workign at 19,200 with an approximate character (byte) transfer rate
of 1350 characters per second. Having that working well makes it much
easier to add software, work on it in multiple environments, and in
general take a more controlled and timely approach to moving files
around.

d. I am now looking at adding either NetBurner Serial to Ethernet
devices or perhaps Zigbee Serial to Wireless Ethernet devices to the
S-100 system both for the console port that currently uses a Wyse
Wy-50 terminal as well as for the "modem" port driven by MDM727 and
the comparable DOS/65 software. That would give me a lot more latitude
in physical placement of the system as well as ability to do things
with it from multiple places in the house by using the home network
(both wired and wireless) for connectivity. Anybody have experience
with these devices?

e. I had not finished the revised 6502 CPU schematic as I was missing
a key sheet. I found that yesterday so I should be able to finish it
in a few days. I need to re-copy some of the sheets as I was using a
Sharpie to do the markups and the sheets were just getting too messy.

Rich