UPGRADING REPAIRING PCs

Table 4.3 Using LBA Mode
Operating
Drive Size System Use LBA Mode Reason
Using LBA Mode 99
504MB MS-DOS, Yes Drive will be limited to
Windows 9x/ 504MB without LBA
NT/2000, OS/2 mode because of 1,024cylinder
limit
>504MB Linux, UNIX, No No 1,024-cylinder limit
Novell NetWare with these operating systems
Problems with LBA Support in the BIOS
Ideally, LBA mode would be automatically enabled in a clearly
understood way on every system with an enhanced BIOS. And, it
would also be easy to know when you did not need to use it.
Unfortunately, this is often not the case.
Many 1994–1996 versions of the AMI text-based and graphical
(WinBIOS) BIOSs listed the basic hard drive geometry on one
screen and listed the LBA mode option on a different screen altogether.
To make matters worse, the automatic drive setup options
on many of these BIOSs didn’t set the LBA mode for you; you had
to find it and then set it. But perhaps the worst problem of all was
for users who had carefully set the LBA mode and then ran into
problems with other BIOS configurations. Most AMI BIOS versions
offer a feature called Automatic configuration with either
BIOS/Optimal defaults (high performance) or Power-On/Fail-Safe
defaults (low performance). In AMI BIOSs in which the LBA mode
was not listed on the same screen with the hard disk geometry, any
automatic configuration would reset LBA mode to its default
setting—off.
Because the location of the LBA setting can vary from system to
system, always verify that LBA mode is still enabled if you make
any changes to a BIOS configuration on systems that use LBA
mode.
Dangers of Altering Translation Settings
Depending on the operating system and drive configuration, one of
several unpleasant events takes place when LBA translation is
turned off after a drive is configured using LBA. Table 4.4 summarizes
these problems—some of which can be fatal to data!