Useful information relating to greater than
504MByte IDE Hard Drives
If a hard drive with a formatted capacity of greater than 504MB is
installed in a machine that has large hard drive support (also known as ECHS or LBA), then
the full drive size may be utilised, i.e. 540MB, 730MB and 1GB IDE drives.
If the large drive support is disabled in the BIOS setup then the
following will happen.
When the MS-DOS command SCANDISK is run it will report that all data on
the hard disk drive above 504MB is faulty. This has caused a number of users to call
engineers out to replace these 'faulty' drives.
There is nothing wrong with the drive. This can be demonstrated by
enabling the large hard drive support again and re-running the SCANDISK command.
The reason for this problem can be explained as follows;
A Quantum 540MB drive has 540,000,000 bytes of data
(Quantum equate 1,000,000 bytes to a Megabyte), When correctly expressed this equates to
515MB (540,000,000/1,048,576)
(There are actually 1,048,576 bytes in a Megabyte)
When the extended drive support is turned off the drive is effectively only a 504MB drive.
Thus SCANDISK will report the difference between 515MB and 504MB (11MB) as being defective
data that requires repair.
It should be noted that if an IDE hard drive greater than 504MB is to be
installed in a machine equipped with large drive support, it should be formatted and used
with the large drive support turned on. Otherwise the situation outlined above may occur. |
