Xerox 820 system disks in Teledisk format?

[Fred Cisin]

> > because the stock PC hardware supports a max of 4 drives.  Any more
> > requires after-market hardware that is not standardized.
> >>    seeing if it would talk to the Compaticard FDC.  It won't.
> >> Now that I know it doesn't support anything but the NEC 765, I'll have to
> > The Compaticard IS NEC 765 (or indistinguishable copy)

On Tue, 5 May 2009, Steven Hirsch wrote:
> Then I'm at a loss as to what the problem is.  I can configure the system
> such that the Compaticard is the primary controller (disable the on-board
> FDC in the BIOS).  The first 8" drive is unit 2 (in 0..3) and mapped as
> drive D:.

Compaticard has a few more options than the stock controller, but is
basically just a stock controller without all of the limitations that were
made in IBM's board (such as being hardwired for double density)

I don't have experience with IMD.  Yet.  One of these days when there's
some free time, . . .
BUT, I see a potential problem, based on my own software interface.
You say "mapped", and I'm assuming that you mean DOS drive letter.  Too
many things, such as device drivers, affect the DOS drive letter mapping.
What IMD NEEDS TO KNOW isn't the DOS drive letter, it's the unit number
(0..3), which you've identified as #2.
If you tell IMD "D:", is it thinking that that is unit #3?
IFF you're machine is configured with 4 floppies, and THEN hard disks,
(which is how I prefer to configure my machines)
then floppies would be A: ... D:, followed by hard disk as E:
But some MICROS~1 stuff is hard wired for boot and hard disk being C:

Try a NON-DESTRUCTIVE test, telling IMD to access C:, and see if that
operates unit #2


> I did try lying to IMD and telling it that drive was 1.2, but
> testfdc immediately returns an error without anything obvious having
> happened.
> In the IMD application itself, I can select format and it loads the heads,
> pauses a moment and returns a "write protect" error.

I don't mean to be patronizing, but are you aware that 8" write protect is
opposite of 5.25"?  8" is write protected when the notch is OPEN.

Irrelevant trivia: In "The Computer Bowl" quiz show, NOBODY on Bill Gates'
team could remember where the write protect notch was on 8" disks!
It is where loose tabs can do the most damage.

> That's about when I threw in the towel.  The drive and card work perfectly
> under Teledisk, 22disk, etc, etc. and I was able to write a usable boot
> disk on it after a kind list member sent me a TD0 image.

If you've got a little time, it still would be worth tracking down what is
happening.

--
Grumpy Ol' Fred     		cisin at xenosoft.com