Upgrading early BIOS - Drive Overlay

[Chuck Guzis]

On 11 Aug 2008 at 18:14, Michael Lee wrote:

> Remember there were also the utilities to fool the PC into using larger 
> sized disks, but I never liked those at all.  Most hard drives in that 
> time period came with the Ontrack, EZDrive, Disk Manager, MaxBlast, 
> programs.  The Disk Drive Oveylay programs do a software convert of the 
> BIOS settings and actual settings and make it boot/work, usually.  These 
> altered the MBR to sit there, and these have their issues and were 
> always a last resort.  The drives do NOT swap into other machines well, 
> and any issue, esp with the MBR would pretty much cause a FAIL.

The  "disk managers" usually just install their own memory-resident 
drivers from the first track of the hard drive, then conceal that 
first track from view.  The shortcoming was that (a) it cost some RAM 
and (b) if you used an OS that was unaware of the drive overlay, 
things could get pretty screwed up.

ISTR that there was also a BIOS extension ROM card that plugged into 
an ISA slot to provide the necessary functionality.  

Most of those disk manager programs were distributed with hard disks 
and so are keyed to the manufacturer's branding returned by an 
IDENTIFY command.  Somewhere around here, I think I've got a real 
retail copy of a generic Ontrack Disk Manager.

Cheers,
Chuck