Hardware Reference
In-Depth Information
Total Bytes 4,227,858,432 4,227,858,432 4,227,858,432
Megabytes (MB) 4,228 4,228 4,228
Mebibytes (MiB) 4,032 4,032 4,032
Gigabytes (GB) 4.23 4.23 4.23
Gibibytes (GiB) 3.94 3.94 3.94
However, if the drive reports a value other than 63 sectors per track or has other than 4,
8, or 16 heads, LBA-assist translation does not result in the same parameters as CHS bit-
shift translation. In the following example, different translations result:
Revised bit-
LBA-assist
P-CHS
shift L-CHS
L-CHS
Parameters
Parameters
Parameters
——————————————————————————————-
Cylinders 16,383 1,024 1,024
Heads 16 240 255
Sectors/Track 63 63 63
=============================================================
Total Sectors
16,514,064
15,482,880
16,450,560
——————————————————————————————-
Total Bytes 8,455,200,768 7,927,234,560 8,422,686,720
Megabytes (MB) 8,455 7,927 8,423
Mebibytes (MiB) 8,064 7,560 8,033
Gigabytes (GB) 8.46 7.93 8.42
Gibibytes (GiB) 7.87 7.38 7.84
The LBA-assist translation supports 8.42GB, which is nearly 500MB more than the re-
vised CHS bit-shift translation. More importantly, these translations are different, which
can result in problems if you change translation modes with data on the drive. If you were
tosetupandformatadriveusingCHSbit-shift translation andthenchangetoLBA-assist
translation, the interpreted geometry could change and the drive could then become un-
readable until it is repartitioned and reformatted (which would destroy all the data). Bot-
tom line: After you select a translation method, don't plan on changing it unless you have
your data securely backed up.
Virtually all PC BIOSs since 1994 have translation capability in the BIOS Setup, and vir-
tually all offer both translation modes as well as an option to disable translation entirely.
If both CHS bit-shift and LBA-assist translation modes are offered, you should probably
choose the LBA method of translation because it is the more efficient and flexible of the
two.LBA-assist translation alsogetsaroundthe4.2GBoperatingsystembugbecauseitis
designed to allow a maximum of 255 logical heads no matter what.
You usually can tell whether your BIOS supports translation by the capability to specify
more than 1,024 cylinders in the BIOS Setup, although this can be misleading. The best
clueistolookforthetranslationsettingparametersintheATA/IDEdrivesetuppageinthe
