Re: Need help with bootable CP/M disk
- From: "Herb Johnson" <noone@xxxxxxxxxxxxxxxxxxx>
- Date: 14 Jul 2005 08:01:15 -0700
Kevin wrote:
> I seem to have a catch-22 problem. I'm trying to get an
> 8080-cpu S-100 system running cp/m, but I don't have a
> working S-100 cp/m system to make a bootable disk, and I'm
> not sure I have the right code to bootstrap a disk anyway-
> need a working disk to test it.
>
> The System: 2 MHz, S-100 8080 cpu, with a 32K byte ram board
> and 2 8 Kbyte ram boards. I have a looks-like-it- was-new
> Versafloppy II card. I am using a standard 1.44MB, 3.5" pc
> floppy drive as my cp/m drive for this system (see below).
> Also, a SSM video card and hex LED display board which works
> with my eprom monitor code to give me information about
> register amd memory contents, etc.
I can't add much to the comments posted by Mac Scane, who also got a
Versafloppy II card and docs from me, as you apparently did. Those docs
include notes by Bruce Jones about how to use 8080 code in a number of
ways to access floppy controllers including the VF II.
Since you have a running system with hex monitor, you should be able to
hand-assemble and enter in test code to read and write to the floppy
drive. Try some code to simply read the very first sector on side 0 -
formatting the diskette on another system, and noting how big the
sector should be when you try to read it. It does not matter if the
disks is "MS-DOS" formatted, you are only looking at sectors and
tracks.
At the least, your code should be able to move the drive's head from
track to track, light the drive light, that sort of thing. It's
valuable to do these kinds of tests to assure yourself you have
"access" to the drive and controller card. I offer limited information
on specific 3.5" floppy drives, but other sites and the Web may have
more info. Or try working with an old 5.25 inch 360K drive to get
things working. As Bruce's notes indicate, a 2MHz 8080 is challenged to
work at a 3.5" drive's "high density" data rate.
If your CPU card does not generate "phase 0" clock on the appropriate
S-100 pin of the VF II card, you need to add an inverter chip and read
the "phase 1" clock line. My schematics are marked up for this option.
If you want to contact Bruce, contact me and I will pass your inquiry
along.
(Bruce discussed his work some time ago in comp.os.cpm; many of his
notes are available for free download from my Web site, and I sell a
complete set of his notes, code, docs and the Versafloppy II card from
my S-100 Web site at the link below.
http://retrotechnology.com/herbs_stuff/s_sd.html )
Herb Johnson
Herbert R. Johnson, voice 609-771-1503, New Jersey USA
<a href="http://retrotechnology.com/herbs_stuff/";> web site</a>
<a href="http://retrotechnology.net/herbs_stuff/";> domain mirror</a>
** hjohnson@xxxxxxxx and njcc.com/~hjohnson are EXPIRED **
my email address: herbjohnson ATT comcast DOTT net
if no reply, wait & try: hjohnson AAT retrotechnology DOTT com "Herb's
Stuff": old Mac, SGI, 8-inch floppy drives
S-100 IMSAI Altair computers, docs, by "Dr. S-100"
.
- References:
- Need help with bootable CP/M disk
- From: Kevin
- Need help with bootable CP/M disk
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