On 29 Aug 2001, at 0:15, Uzi Paz wrote:

> I'm curious, what is the difference between Generic Hard disk driver
> type46 and generic hard disk driver type80.
>
> Thanks,
> Uzi

  The first PC hard drives relied on one of two technologies to
provide low-level access to the drive and its controller:

1.  Custom boot diskette -- the TallGrass Systems drive/tape units I
was using in about 1983 took this approach.

2.  ROM on the drive controller card -- The IBM PC XT and many
subsequent third-party hard drive systems took this approach.

  Later systems incorporated some generic drive-handling code into
the motherboard BIOS.  To simplify setup, this code included
predefined parameters for a bunch of current drives (typically in the
10-60 MB range), and for many drives you could just configure the
BIOS for type 7, or 23, or whatever "type" matched the geometry (# of
heads, cylinders, and sectors) of the drive you actually had.
  You don't see many drives in that size range any more, but at the
end of the list -- about type 46 or 47 -- was a special entry that
let you fill in the geometry numbers, allowing this scheme to extend
to the larger hard drives that came later.

  So:  A "type 46 generic driver" configures the CMOS for "type 46"
and specifies the actual drive geometry.  It's probably what most
people will find their IDE/EIDE/ATA drives are using.
  I think "type 46" goes with the original list of defined drives
from the IBM AT, copied by most machines since.  I strongly suspect
that you're seeing the "type80" driver listed on a machine whose BIOS
maker chose to extend the list of preconfigured types, so that the
generic type got renumbered to 80, and that Device Manager is
reflecting this in the name it provides for the driver.

David Gillett

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