8" drive on PC troubleshooting

[Fred Cisin]

On Tue, 1 Mar 2005, Dwight K. Elvey wrote:
> >> Wrong step rate! Poke a new on eint othe chip, or does it use the old
> >> table of junk INT 13h used to supoprt?
>
> Hi
>  There is a table that one stores the step rate
> for the drive. You need to alter the value for
> slower drives, like your 8 inch. I forget where
> is it but it is in that lower area someplace
> ( 40:xxx or something ). It isn't a problem
> of the controller. It should work with any controller,
> you just need to find the table and change it.
> It has been a while since I've fiddle with it
> to make my drives step with less noise ( and wear ).
> Dwight

While the default table is often in low memory,
sometimes it is even in ROM.
It is pointed to by INT1Eh.
To alter values in the table, copy it, alter the copy,
then repoint INT1Eh to point to the new address.
Be sure to restore INT1Eh when you are done,
or INT13h may encounter serious difficulties.

If you've got a copy of the PC Technical Reference Manual,
most of the disk parameter table is documented right after INT13h.

--
Grumpy Ol' Fred     		cisin at xenosoft.com