Differences between model 1, 3 and 4

[Abmvk]

I am searching online, but most I find is rather high level. I am looking for details, as much as possible. For example, I just found out that the disk basic of the model 1 has the SET and RESET command, but the disc basic of the model 4 does not. And (my) model 4 has no BASIC in ROM, where the model 1 does.

But well, really any source of detailed comparisons would be appreciated!

 

[TRS-80.com]

I suspect the best resource would be to just look at the Radio Shack catalogs back in the day.

An archive of RadioShack Catalogs (1939-2011)

Flip-through every RadioShack electronics & computer catalog. These catalogs include vintage electronics, stereos, speakers, CB radios, tube radios, computers, communication equipment, electronic test equipment, gadgets, technology & more!

radioshackcatalogs.com

 

[Eudimorphodon]

And (my) model 4 has no BASIC in ROM, where the model 1 does.

Do you have a Model 4P? Regular desktop Model 4s have Model III basic in ROM, just hold down the BREAK key when you turn it on. (Or boot a Model III DOS.)

Short version of the response to this question: a Model 4 booted into a Model 4 DOS is a *completely* different computer from the Model I and III. (Those two are mostly alike.)

 

[Abmvk]

I have a model 4, not the portable, as far as I can determine. And it doesn't boot to Basic, even when I hold down the BREAK key. At least, I don't think so. Minutes after my initial post the computer was producing white smoke, so there is some repairing to do first.

 

[ldkraemer]

That was likely the Square RIFA Cap(s) blowing on the Power Supply.
They should be replaced ASAP.

If it's a TANDY Power Supply versus ASTEC, you need to remove it and check the
Row of Pins for little rings around each pin. Then re-flow the solder for each pin with
some KESTER 63/37 Solder. That will fix the Tandy Power Supply.


Larry

 

[gp2000]

All Model 4's except the portable 4P have BASIC in ROM. If your Model 4 wasn't going into ROM BASIC when you hold down the BREAK key on boot there are only a few possibilities.

• You actually have a 4P (if the diskettes are oriented vertically it's a 4P). Or show us a picture.
• The BREAK key is broken.
• You didn't hold down the BREAK key before powering on or resetting the machine.
• Something quite unusual is going on.

The Model 4 wikipedia page shows the difference between the models pretty well:
https://en.wikipedia.org/wiki/TRS-80_Model_4

 

[kiwisincebirth]

This wikipedia page has a good overview of changes from Model 1 to 3

TRS-80 - Wikipedia

en.wikipedia.org

Apart from the obvious form factor change and other functional improvements, the main differences from a hardware perspective (IMHO) were the move memory mapped IO (e.g. Disk Controller) from $37Ex into IO address space, which made way for an expanded 14KB ROM. If you search there are many sources of the memory and IO maps, which can be compared. I think this was the biggest areas of incompatibility requiring minor software changes.