Re: Microsoft Softcard problems

[nparker@cie.uoregon.edu (Neil Parker)]

In article <1993Jan25.152731.18915@aio.jsc.nasa.gov> mark@pokey.jsc.nasa.gov
(Mark Manning) writes:
>I have a CP/M card on my //e.  The reason I haven't transferred it to
>the //gs is because the layout of the //gs is incompatible with what
>the Microsoft card expects.
>
>If you are unfamiliar with how the Softcard works, here is how:  Like other
>cards for the Apple, the Softcard works on the off cycle of the Apple.  Or
>in other words - the Apple computer produces a squared sine wave.  When the
>wave is at one - the Apple computer does its work.  When the wave is at
>zero, everything else does its work (including the Softcard).  Well, to make
>a long story short - the Softcard expects the wave to be X long whereas
>the //gs' wave is slightly shorter (or Y long).  The difference causes the
>Softcard to go out of sync.  Now, this could all be a bunch of bunk.  I'm
>not an electrician or a EEE person.  But I know about the sine wave, how it
>works, and how it affects various things.  I also know that even in slow
>mode the //gs is still faster than the //e.  Thus, it stands to reason that
>the Softcard (which was made to ][+ standards) will not work properly on a
>//gs.  It works ok on a //e (though every now and then it won't boot for
>the same reason).

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).

I still suspect heat may be a factor...the card gets really hot after a
failure.

>Your best bet is, if you want CP/M, to get a much newer card which was made
>for the //e (or //gs).  If you are determined to use the Softcard, then I
>would suggest turning off any kind of an accelerator you might have and
>placing the system into its slowest mode.  This will help the Softcard with
>trying to work with your system.

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...

>Keyboard problem:
>
>The CP/M card has its own memory.  Certain of these memory locations were
>mapped via ROM into specific places in the ][+'s memory so things like
>reading the keyboard, writing to the disk drive, etc... could be accomplished
>easily.  Unfortunately, these are not the same _exact_ memory locations
>in the //gs anymore (which is why some DOS 3.3 programs do not work
>properly under ProDOS).  Since the //gs does not read a keyboard in the
>same manner as the //e did, it is to be expected that the Softcard would
>have problems with this (and other things).  Again, your best bet is to
>sell the Softcard and buy a CP/M card which is made for the //gs.

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.

Perhaps the Z-80 is generating some kind of false read that hits 0E010H
($C010 in the 6502 memory map)?

>Of course, if you were REALLY industrious (sp?) you could rewrite the
>CP/M operating system so it would allow for these changes.  No? ;)

Not really necessary...the CP/M console driver is smart enough to notice
that I have the 80-column firmware turned on, and it calls the firmware to
do all its keyboard and video I/O.  I was just a bit bothered by the Z-80's
inability to bypass the 80-column firmware and read the keyboard directly.

               - Neil Parker
--
Neil Parker                 No cute ASCII art...no cute quote...no cute
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