Hi pat,
I too just picked up a model 4. I didn't get any disks but mine
says "Disk?" when I power it up. I opened it up and mine is a basic 64k
machine with two SS disk drives. The drives in mine are made by Texas
(somebody), Texas Peripherals maybe? I checked and they're 40 track SS
The Texas Peripherals drives are _exact_ copies of Tandon drives (same
schematics, same PCB layouts, same mechanical bits. I've swapped
mechanical parts between Texas Peripherals and Tandon drives, and I use
the repair info in the M3 manual for Tandon drives too...
They almost certainly are the origianl drives. Or at least Texas
Peripheral drives were used by Radio Shack...
drives. I believe these are the original disk drives
for the M4 but I've
been told that they will support 80 track and DS drives. But I don't
know if you had to patch the BIOS and/or OS to do that.
The bootstrap ROM (there's no real ROM BIOS in these machines) expects to
boot from a single-sided disk in a 40 cylinder drive. Most people kept
drive 0 as a 40 cylinder unit for this reason.
To use DS or 80 cylinder drives you have type a couple of commands if
you're using a sensible OS like TRS-DOS 6 (== LSDOS). If you're running
one of the M3 OSes, then you might have to patch things....
-tony