Taken from StorageReview.com ...
33.8GB Barrier (also known as 32GB Barrier)
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This is a relatively new hard disk barrier that showed up in early 1999. It is yet another in a long series of limits caused by the inability of a BIOS version or type to handle a particular number of cylinders, much like several smaller barriers have been. It is often called the "32 GB size barrier", which is approximately correct anyway.
In this particular case, some versions of Award BIOS cannot handle drives that have more than 65,535 cylinders. Since hard disk parameters usually use 16 heads and 63 sectors, this works out to a capacity of about 33.8 GB or 31.5 GiB before trouble occurs. As of about June 1999, this problem had been corrected, so it is most likely to show up on systems purchased before that month.
I must say that I find this to be a rather strange hard disk barrier, because hard disks above about 8 GB in size no longer really use discrete geometry for access; they are instead addressed using LBA and a flat sector number from 0 to one less than the number of sectors on the drive. This 65,536 cylinder problem must be a remnant of some older code, or something related to compatibility with older hard drives. Regardless of its origin, many system owners will have to deal with it.
To get around past hard disk barriers, most modern hard disks are now no longer addressed using discrete geometry (cylinder, head and sector numbers) but rather logical block addressing and a sector number. In the case of the ATA interface, 28 bits are used for the sector number interface between the operating system, BIOS and the hard disk. This means a hard disk can have a maximum of 2^28 or 268,435,456 sectors of 512 bytes. This puts the ATA interface maximum at 128 GiB or approximately 137.4 GB.
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>> LBA was available with ATA33 interface onwards, hence support for hard drives up to 137GB.