The use of logical hard disk geometry gets around the problem that physical hard disk
geometries cannot be properly expressed using simple BIOS settings. Logical geometries
don't go far enough, however. In most cases, higher levels of translation are needed as
well, because other problems relating to old design decisions make it impossible for even
the logical geometry to be used with modern large hard disks. These are the infamous BIOS capacity barriers such as the 504 MB limit on standard
IDE/ATA hard disks, the 8.4 GB limit for standard Int 13h BIOS addressing, and other
similar issues.
In order to get around these barriers, another layer of translation is often applied on
top of the geometry translation that occurs inside the hard disk. This translation is
performed by the BIOS (or sometimes, third-party overlay software.) There are many issues
involved in BIOS-level translation; the matter is discussed in
detail here.
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Management and Recovery
