TRS-80 Model 4 help requested

From: Al Hartman <alhartman_at_yahoo.com>
Date: Thu Feb 27 13:24:01 2003

> From: Patrick Finnegan <pat_at_purdueriots.com>
>
>
> 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
Received on Thu Feb 27 2003 - 13:24:01 GMT