Turbodos on a Horizon 8/16 system

Dave Dunfield dave06a at dunfield.com
Sun Feb 18 04:39:06 CST 2007

> I first booted into HDOS from floppy, the hard disk version of NSDOS. 
> It has both non-destructive and destructive disk tests.  "LI" shows that 
> there is no meaningful HDOS file system on the drive.
> Next, I ran only the non-destructive test since one goal is to see what 
> is on the hard disk.  HDOS, like NSDOS, has a command for reading 
> arbitrary absolute sectors from the floppy, but it isn't supported on 
> the hard drive -- instead you can load sectors relative to a named file, 
> which doesn't help me here.
> Next I booted turbodos from floppy.  "DIR" shows no meaningful file 
> system on either of the two partitions on the drive.
> Finally, I'm at an impasse.  I assume that this system had *something* 
> on the drive, although I suppose a previous owner did a FORMAT on the 
> drive before passing the system on.  It would be easiest for me to just 
> format the drive and install either HDOS, or more likely, TurboDos and 
> get on with it.  If I had more time I'd look into finding a mechanism to 
> read the hard drive sector by sector and make a copy, but the reality is 
> I have more projects than I have time for, so this seems unlikely.
> Does anybody who has read this far have an idea what to do next?  Format 
> and reinstall?  Write my own driver to dump the disk first?  Find an old 
> PC with a controller card that could interface to the drive?

Why not write a small program (on floppy) to read arbitrary sectors from
the hard drive and dump them out. I've never used HDOS (all of my N* systems
are floppy only), however I would expect that it's not hard. According to my
TurboDOS manual, T-function 22 provides for physical disk access.

Many XT and early AT controllers used the ST506 interface, however I don't
know if the N* controller uses a compatible format - it shouldn't hurt to
try as long as you don't write to the drive.


dave06a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Collector of vintage computing equipment:

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