TRS-80 Model 1 vs Model III disk/application compatibility

[Tony Duell]

> > As far as I rememebr, a Model 3 will not boot any Model 1 disk (or of
> > course vice versa).
> 
> OK.  That makes sense and answers one question I had.

IIRc, the Model 3 can physically read any M1 disk, although it can't
necessarily write them (The M1 used one of the 1771's 'extra' data markers
on the directory cylinder, which later disk cotnrollers couldn't write). 
I cn't rememebr about OS compatibility -- LDOS, which is what I mostly 
use can read M1 TRS-DOS or LDOS disks on a model 3, but I have an idea 
TRS-DOS won't. And binary programs generally won't run on the other 
machine -- almost all the OS routines changed their addresses :-(

> I have not yet tried to make backups.  I have all the docs so backups should
> be not difficult to do once I dig out a box of SSSD blanks from the back of the
> closet.

Actually, the M3 has a double-density disk controller (1793 IIRC), and by 
defualt it used double-density encoding on the disks. It can do single 
density as well, though (although, IIRC, TRS-DOS 1.3 uses double density 
only). So you want SSDD or DSDD blank disks. The sort of disks that are 
called '360K' on a PC work fine.

Again, IRIC, TRS-DOS 1.3 pretty much restircts you to 40 tracks 
single-sided. Other OSes let you do anything the drives are capable of. 

> One thing I'm not sure of with the Enchanter original is that since
> it's marked "side 1"
> and "side 2", but I don't have the box or the box insert, I can't tell

I assume this is a 'flippy' disk.

> what platform it's for.
> It _is_ marked "TRS-80", but I don't recall seeing a model number
> mentioned on the
> label.  The Zork game file is somewhere between about 70K-85K.  Enchanter is
> almost certainly over 80K (I'd have to find a copy to check), so I guess I'm not
> surprised to see that it overflows one side of a TRS-80 SSSD disk, but I am

The M3 is double density, with about 180K per side. Not all of that space 
is avaiallbe for user programs, of course.

-tony