Hard Disk Utility
- Will format your hard disk so it can receive new
partitions.
IT WILL SMASH EVERYTHING ON YOUR HARD
DISK!!! USE WITH CAUTION. A lot of inexperienced
users have lost their sanity with this one. Several
computer stores have made extra money with it! There's no
need to do this unless you experience errors or if you
want to change the interleave. DON'T TOUCH THIS IF YOU
HAVE AN IDE DRIVE. It will perform a low level format
and probably SCRAP your IDE hard drive. IDE is the
standard drive type that nearly everyone has now. SCSI or ESDI
drives shouldn't be low-level formatted. The new drives
actually don't perform the low level format, but some old
AT-Bus (IDE) drives you can scratch with this... This
entry is only sensible for old MFM or RLL hard disks!
Please refer to your hard disk manual to see how or if
your hard disk can be low level formatted. Don't tell us
we did not warn you. 
Many manufacturers provide utilities to low
level format their IDE drives (or any other types).
Please refer to the comp.sys.ibm.pc.hardware.storage
FAQ for more technical information about this procedure. If
normal (high level) hard disk formatting is required, you
can use DOS FDISK to first erase and create partitions
and then use FORMAT. It is also a good idea when you hard
disk becomes inaccessible to see if it is just the system
files that are corrupted. Most of the time, it is the
case. SYS will do the job of replacing system files.
Several packages (PC-Tools, Norton, etc.) provide
utilities for repairing "damaged" HDD and FDD. Therefore,
low level format is always of LAST RESORT when you
encounter HDD problems.
- Handy when you "forgot" the specs of your hard
drive. The BIOS will detect the number of cylinders,
heads and sectors on your hard disk. In some BIOS
versions, this option in the main SETUP menu.
- Determines the optimum interleave factor for older hard
disks. Some controllers are faster than others, and you don't want
the sectors laid out so reading consecutive sectors
usually results in just missing the sector you wanted and having
to wait a whole disk rotation for it to come around
again. On modern ones, it's always 1:1 (and even if it wasn't,
you cannot reformat anyway).
- Interleaving is specified in a ratio, n:1, for small
positive integers n. Basically, it means that the next
sector on the track is located n positions after the
current sector. The idea is that data on a hard drive
might spin past the heads faster than the adapter can
feed it to the host. If it takes you more than a certain
amount of time to read a sector, by the time you're ready
for the next sector, the heads will have passed it
already. If this is the case, the interleave is said to
be "too tight". The converse, where the CPU
spends more time than necessary waiting for the next
sector to spin under the heads, is too "loose"
of an interleave. Clearly, it is better to have too loose
an interleave than too tight, but the proper interleave
is better still. Especially since any controller with
read-ahead cacheing can pull the whole track into its
buffer, no matter how slow the CPU is about fetching the
data down.
- The 1:1 interleave arranges the sectors on a track as
follows:
- 0 1 2 3 4 5 6 7 8 9 a b c d e f g (17-sectors, using base
17 for convenience, this is clearly the in-order arrangement, one
after another)
- This is 2:1 interleaving:
- 0 9 1 a 2 b 3 c 4 d 5 e 6 f 7 g 8
- The CPU has a whole sector's worth of time to get the a
sector's data taken care of before the next sector arrives.
It shows which logical sector goes in each physical
sector.
- Anyway, an n:1 interleave restricts the transfer rate to
1/n the speed of a 1:1 interleave (which is better than 1 revolution
per sector if the interleave is too tight!). No modern PC
should require interleaving. Only MFM and RLL (maybe also
ESDI) and floppy drives which are capable of it (you
could format a 1.44 meg floppy to 21 sectors/track, which
would require a 2:1 interleave to not exceed the 500 mbps
speed of the controller...but why?).
- Scan the hard disk for bad blocks. It is
performing a LOW LEVEL FORMAT on the track where bad sector
is encountered to mark that sector as a bad. It could
cause damage on user data, even if scanning itself is non-destructive
(also on MFM, RLL disks). Therefore, DON'T USE
this option to on AT-Bus (IDE), SCSI or ESDI drives.
These drives store the bad block data themselves, so you
don't have to tell them or scan the media! Recommendation:
use a media analysis program provided by an utility
package or your hard drive manufacturer.