Microport Sys V and hard disks

[Daniel M. Frank]

---------

   After hearing about (and experiencing myself) all the problems people
have installing Xenix on an AT or compatible with anything but the IBM
standard hard disks, I was gratified to discover that Microport did it
right.

   The way it works is, when you run their hard disk setup program, it
asks if you want to use the default parameters or supply your own.  If
you elect to supply your own, they get written at the beginning of the
alternate track table, for later use by the hard disk drivers.

   How, you ask, do the hard disk drivers find the table?  Sound like
Catch-22?  Turns out that the DOS partition table has some very specific
data on where the first and last sectors of a partition are.  It gives
head, sector, and cylinder.  If you put your parms in the first or last
sector of a partition, your driver can find them by:

   * Reading the first block of the disk (head 0, sector 1, cylinder 0).

   * Using the numbers in the table to read the bad track table with
     the parameters in it.

   * Using those parameters to access the rest of the partition.

   Very clever, eh?  You'd think Microsoft, the people who wrote DOS,
might have a clue.  Oh, well.

   So, if you plan to use non-standard hard disks (this includes the
disks in a Compaq, as well as hard cards, great big disks, etc.),
get the Microport system.  You'll have much more hair when the installation
is over.


-- 
	Dan Frank
	    ... uwvax!geowhiz!netzer!prairie!dan
	    -or- dan at caseus.wisc.edu