Re: Microsoft Softcard problems

[mark@pokey.jsc.nasa.gov (Mark Manning)]

> I may be displaying my own ignorance of electronics here, but if it were
> really a timing problem like this, wouldn't the card fail to work at all in
> my GS?  It DOES work, for an hour or so, as long as I set the system speed
> to 1 MHz (the CP/M boot disk can't even find the card if the speed is any
> faster than that).

It isn't ignorance on either of our parts.  I've worked on computer hardware
from Univac 1108s to Atari's and I've found that a lot of machines can
withstand variances in timing as well as many other things.  Not that I'm
an electrician mind you.  I just have a nack for working with the things. :)

My Softcard also heats up quite a bit in the //e though not as much as yours
seems to in the //gs.  As an experiment (if you think this is heat related)
get a regular fan, take the cover off of your //gs, and let it blow air
over the boards while you try it.  If it helps - then it must be the heat.
If it doesn't - I'd stick with the timing problem theory.

> Do you really think anybody out there would want to buy it?  The only
> reason I ended up with it is that somebody was giving it away for free...
> 

Some schools would still (even with the advent of the Macs and the 386s/486s)
be willing to buy the card for a modest price.  I wasn't thinking of $200-up
amounts.  I was thinking in the $10-$50 range.  That would help you to get
one of the better boards.  Also, there are CP/M enthusiasts (sp?) out there.
Look under the comp.sys.cpm area.  Also, those people would probably be better
able to answer your questions than here (since they are geared towards CP/M
and this area is geared towards DOS 3.3 and ProDOS questions).

> As far as I can tell, there is no memory at all on my Softcard, and the
> documentation states that the Softcard uses the Apple's memory, remapped
> somewhat so that the CP/M program area isn't sitting on top of the 6502
> stack and video areas.  I've been careful to take that remapping into
> account in my experimenting.  The keyboard ($C000) shows up at Z-80 address
> 0E000H, all except for the high bit, which always seems to be 0 whether
> or not a key was pressed.  This curious missing bit doesn't seem to affect
> any of the other I/O areas...I have no problem reading meaningful data out
> of other I/O locations.

In my manual for the Softcard I remember reading that the Softcard has its
own 64k on the card which it uses to store all of whatever it is doing.  This
was then moved to the 64k on the motherboard in an "as needed" basis.  I could
be wrong.  After all, I've read so many manuals they tend to start merging
together.  So it could very well have been a different manual about a different
card.  Going on the tenuous basis that what I remember is correct though - the
various locations which were written to the Apple's memory dealt with graphics,
text, and the turning on and off of the various external devices (such as the
monitor's 40/80 columns, the disk drives, modem, and other such devices).  This
could be entirely wrong though.  What I _really_ need to do is to find and get
out my Softcard manual so I could go over this correctly - rather than trying to
remember this. :)
> 
> Perhaps the Z-80 is generating some kind of false read that hits 0E010H
> ($C010 in the 6502 memory map)?

I believe this "false read" is really related to the timing/heat problem.  If
you can solve the timing/heat problem - the rest might go away.  But there is
still a question of "is the //gs so different that CP/M can't run on it?"

But I'll tell you what!  This weekend I'll try to remember to yank out my CP/M
card from the //e as well as the disk drives (5.25") and I'll move all it over
to the //gs.  Then I'll try out some stuff on the //gs, let it run for an hour
or two, and see what happens with it.  Then I'll report back to you about my
findings.  Maybe I'll run into the same stuff.  If so, I'll let you know what
happens and maybe we can figure this out together.  Sound good?