22 Feb
2022
22 Feb
'22
6:17 p.m.
On Tue, 22 Feb 2022, Bill Gunshannon via cctalk wrote:
Hmmm.. I wonder if I could do any of this with my OS9
system
running on a Tandy COCO? Lot's of ability to fudge with disk
formats and you can't find a controller much older. :-)
Makes me wonder about the other old TRS80's. All handle 5.25
floppies and have old controllers. And OSes that let you do
pretty much anything you want. Even shoot yourself in the foot.
I wonder if I even have any RX50 floppies laying still around
here anywhere?
Certainly!
The Coco used a Western Digital 179x controller. I don't remember which
specific one, and for simple stuff like this, it won't matter much.
The WD doesn't have the "flash blindness" that sometimes interferes with
the NEC 765 series when reading disks where the first sector is too soon
after the index pulse.
The WD has a semi-raw track read that is real handy (The NEC has a
multiple sector read, but not a raw track read)
There have been some programs on the Coco for reading and writing some
other formats. ISTR Dr. Marty did one on the Coco for reading PC disks.
(probably published in Rainbow)
The TRS80 Model 3 and 4 also used 179x controllers. With very different
operating systems (The Randy Cook family of OS). Look for "TRSCross"?, by
Mike Gingel, as a program running on TRS80.
Also, "Trakcess" is very handy for analyzing disks, although you need to
do some trivial mods to it for double sided, etc.
Looking at the program of Trakcess will make it easy to get the basics
to do almost anything that you want to do.
William Barden did a nice pamphlet on disk I/O for TRS80.
Then Harv (HC) Pennington wrote very extensively about the internals of
TRS-DOS.
Until August 1981, when the 5150 came out, my disk format conversion work
was on TRS80.
The TRS80 model 1 used the 1771 controller which was single density only.
And, the original SA400 single sided drive on it only got 35 tracks.
Be careful, the second side signal on the cable is used on the Model 1 as
drive select for the fourth drive! (Tandy wasn't planning on DS drives)
But, the retrofit "Doubler" added a 179x controller.
As a REAL programmer, you can shoot yourself in the foot with any language
or operating system! (Is that the definition of programmer?)
--
Grumpy Ol' Fred cisin at xenosoft.com