xenix redux (or, how to bring back a dead xenix pc)

Christian Corti cc at informatik.uni-stuttgart.de
Sat Jan 17 14:01:20 CST 2009

On Sat, 17 Jan 2009, Brad Parker wrote:
> Inside is a 386 with about 4mb of ram and a Compaq ESDI controller.  And
> a dead Dallas clock chip.
> I dremel tooled the Dallas clock chip and soldered in a new battery
> pack.  I got a floppy disk image to reset the bios from someone here
> (thanks!)  But despite many tries it would not boot.  The diag program
> would not let me set the disk parameters exactly the way they needed to
> be set.  most frustrating.

Well, ESDI controller are so-called intelligent controllers. You can't 
(and must not) set the drive parameters in the BIOS. Instead (at least 
with the WD or Adaptec ESDI controllers) you have to select drive type 1. 
The controller knows the drive parameters as they are read from the drive. 
And the controller BIOS doesn't care about the BIOS drive geometry, it 
used the values from the drive.
What exactly is the problem with booting? Any special error codes?
Don't forget to disable the onboard hard disk interface, if available. If 
the board has e.g. an onboard IDE interface, a BIOS reset would most 
probably enable it, and the resources would collide with those of the ESDI 

> I then put the resulting disk image on another linux box and wrote a
> tiny C program to search for valid sysv super blocks.  It found 3.  I
> then used "dd" to copy part of the image, with an offset (the start of
> the first superblock), to a new file.

Or you could just write the disk image back e.g. to an IDE disk and put 
that into the old PC.

> and viola!  I could see all the files and could make a tar file of
That's a music instrument, I think you meant voilà ;-)


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