TRS-80 Model 4 help requested - test-drb@ccmp.vtda.org

27 Feb 2003

...
  From: Patrick Finnegan &lt;pat(a)purdueriots.com&gt;

 Umm, actually, 'no'.  The cable has pins removed to
 change drive selects, and the drives don't have any
 method of setting the drive selects.  So,
 swapping the position of the drives changes what
 drive they are.  The LED on the front of the drive
 confirms that. 
If you're that sure. It sounds like you just have bad
boot disks.

Remember, a Model IV needs a boot disk with the Model
IV ROM file on it or else it won't boot properly. It
will only boot CP/M+ for the Model IV without this.

This *MAY* be why you're having a problem booting
stuff..

...
  Is there an easy couple line program I could type up
 in basic that using INP() and OUT() to test the
 drive controller to see if it can read from
 the disk?  I _could_ read the tech manual I have,
 but I tend to be lazy when it comes to re-inventing
 things that other people already have done. 
I don't think so. It might be possible, but I don't
know how to do that.

...
  One last thing, if it matters... it seems my machine
 was upgraded to 128kB RAM.  Is is possible that the
 machine has bad memory that shows up when booting
 from a disk but not when starting up basic? 
If the problem is in the first bank, maybe...

I used to use a simple program to test RAM in the old
days...

I think this will work (If I remember it correctly)

10 A = Mem (0)
20 Print A;" ";
30 gosub 10

What happens here is that the program puts the return
for the gosub on the stack and reduces the RAM by a
few bytes each iteration.

If there is bad ram, the computer will crash.

If not, it will eventually end with an out of memory
error.

Contact me off list. Maybe I can somehow make you a
disk you can boot.

I could probably set up my Coco with a Disk Copy
program to copy the disk.

If my Model I were working, I could use SuperUtility
to make you a bootable disk.

I'm looking for a Model III or IV locally to play
with.

Anyone in Philly have one they'd part with?

I'd certainly use it to help Pat out as a start...

I might have something to trade for it you'd want
(like a 56k Modem for a PC or a low capacity PC IDE
Drive?)

Regards,
Al