TRS-80 Model 4 help requested

From: Patrick Finnegan <>
Date: Thu Feb 27 10:03:01 2003

On Thu, 27 Feb 2003, Al Hartman wrote:

> Ok..
> Take a look at your "1:" drive. Near the connector you
> should see a socket with something that looks kind of
> like a chip in it.
> But, it will have 4 metal bridges and three will be
> broken. On your "0:" drive the first one will be in
> place and 2 - 4 will be broken.
> On the "1:" drive, the first, third and fourth should
> be broken and the second bridged.
> If you swap these between the two drives, you ought to
> be able to turn the "1:" drive to a "0:" drive.

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.

> As for your IBM drive, it is probably jumpered for DS1
> ("1:" drive). If you can find the jumpers on the logic
> board, move the jumper from DS1 to DS0 if you'd like
> to try to use that as the "0:" drive (leaving the "1:"
> drive as-is).

Now, the IBM drive has one of those annoying 'broken-jumper' IC things.
I've circumvented that with a staple for now, and it gets selected

> Let me know if that helps you.

I seem to have no problem with the drive selects. I'm fairly certain that
the drives, their cable, and the disks are good. What's the next thing to

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.

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? I haven't tried any
'test' basic programs yet, so I'm not sure how well basic really works

Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
Received on Thu Feb 27 2003 - 10:03:01 GMT

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