14 Jun
2001
14 Jun
'01
3:17 p.m.
Here are some answers.
It plugs into the PC's ISA bus. Please see the Web page I pointed to
above, and the Catweasel links off of it, for more information.
See links on my Web page to the manufacturer and a couple of other places
you can buy them.
tim.mann(a)compaq.com wrote:
I've updated the cw2dmk program to version
1.6. This is a program that
uses the Catweasel ISA disk controller to read disk formats that are hard
or impossible to read with an ordinary PC floppy disk controller. The
new version adds a few features, among them the ability to read the DEC
RX02 double density format. See http://www.tim-mann.org/trs80resources.html
Jerome Fine replies:
When you mentioned the Catweasel ISA disk controller and compared it to an
ordinary PC floppy disk controller, it sounds like you are suggesting that
it can run on an ordinary PC? Am I correct in this assumption? If so,
is a special driver also required or does the cw2dmk program do everything?
The cw2dmk program talks directly to the Catweasel hardware; no other
driver is used. There are also various other programs/drivers available
for the Catweasel to read other kinds of disks (not from me).
Also, a rather important question, which floppy drive
is used?
Basically any standard floppy drive that is physically capable of accepting
the disk and stepping the head to the tracks. Any standard 8" drive should
work for real RX02 disks, for instance.
By the way, the disks I've actually tested the RX02 support on are in
a slightly modified RX02 format that uses both sides of an 80-track 5.25"
floppy. The encoding is the same unique FM/MFM combination as original
8" RX02 disks, but at half the bit rate. Sectors 1-13 are on the front,
14-26 on the back. They read fine in the standard 5.25" PC drive that
I used (a Teac FD-55GFR).
I do have a real 8" drive (Shugart 850) and have used it to read TRS-80
Model II disks with cw2dmk, but I don't have any 8" RX02 disks to try
in it. However, if you wanted to mail me a couple, I'd be glad to try
reading them to verify that it works. Contact me off-list.
You need a 34- to 50-pin adapter cable to plug an 8" drive into a Catweasel.
I made mine based on the diagrams in the CP/M FAQ; see
http://users.breathemail.net/trevor_gowen/cpm/cpm_faq.htm
If you aren't even enough of a hardware person to be comfortable making
up such a cable, you could try the premade adaptor sold by D Bit:
http://www.dbit.com/fdadap.html
I understand that no ordinary PC floppy disk
controller/drive drive is able to
read/write the DEC RX02 "double density format" since it is really only a
single density header followed by double density data - or something similar.
Right. The Catweasel not a normal PC floppy disk controller; it's a sampler.
With the proper software, it can read just about anything.
It is my understanding that there were third party
Qbus controllers which
used Calcomp 8" floppy drives and that even the DEC RX02 controller
could use the Calcomp drive and be double sided. Is that possible with
the cw2dmk program, namely is an 8" RX03 double-density double-sided
(DSDD) floppy possible?
Yes, it can read both sides if you have a double-sided 8" drive (mine is).
Note that I haven't yet written a program to *write* disks with the Catweasel,
though the hardware has support for it.
Source code is
included under the GPL, so those who prefer to build their
own hardware instead of buying a Catweasel (let's not start *that* debate
again) may find it of some use too.
Since I am not a hardware type, where can I find the Catweasel controller and
a floppy drive so I can read 8" floppy RX02 diskettes on the PC - assuming
that my understanding is correct? And please also help with my question as
to DSDD floppies since more than half of my 8" floppies are DSDD - I used
a DSD 880/30 (Data Systems Design) system on my PDP-11 Qbus system
and modified the driver under RT-11 to also use the other side of the floppy
in the DYX.SYS device driver as well as adding a bounce buffer so that DYX.SYS
could be used under the 22 bit address range of the V5.0x versions of RT-11.
I think I've covered these questions above.
Thanks in advance for any help. I use the PC that I
have available to me
most of
the time now when I run RT-11, so being able to access the 8" floppies would
be
a big plus if this is possible.
Note that cw2dmk just makes an image file of the data (and formatting
information) on the disk. You'll have to write a bit more code to transform
that file into a format that's useful on your PC. That shouldn't be hard.
Tim Mann tim.mann(a)compaq.com http://www.tim-mann.org
Compaq Computer Corporation, Systems Research Center, Palo Alto, CA