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RE: [N8VEM-S100:105] Re: S-100 Motherboard

Rich, FWIW, I have modified Modem 7  to two core files (PCGET & PCPUT) which
I use all the time to move files back & forth between S-100 systems & PC.
It's a stripped down version which just erases an old file of the same name
and waits for new file data to appear at a serial port.  I like use a telnet
program (Absolute Telnet/Celestial Software) in XModem mode.  I use the USB
port on the S-100Computers/N8VEM at ~50K Baud.  Small file downloads are
almost instant! See here for more info.


For multiple files just bunch them together as a .LBR file with the old CPM
"LU" program.

-----Original Message-----
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On
Behalf Of Rich Leary
Sent: Saturday, March 05, 2011 8:39 AM
To: N8VEM-S100
Subject: [N8VEM-S100:105] Re: S-100 Motherboard

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

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.