[ The PC Guide | Troubleshooting and Repair Guide | The
Troubleshooting Expert | Troubleshooting Specific Components
| Troubleshooting Hard Disk Drives | Missing
Space Issues ]
I have a hard disk that is over 540 MB in size but the system is seeing it only as a
504 MB or 528 MB drive
Explanation: The system is not seeing the full size of your hard disk. In
particular, the system is detecting the disk as being either 504 or 528 megabytes
(depending on what piece of software is reporting the size). Other than this, the hard
disk does appear to work.
Diagnosis: The maximum size of an IDE/ATA hard disk running in standard,
untranslated mode is 504 binary megabytes, or 528 decimal megabytes. This is the classic barrier that limits the use of
larger hard disks on older systems. In order to use a disk over 504 MB in size, you
must have a motherboard or hard disk controller capable of BIOS translation, or you must
use a dynamic drive overlay to do the translation in software. If your large disk is
showing up as 504/528 MB, then this means that either your motherboard and BIOS do not
have translation support, or that support has not been enabled.
- When you see this smaller size of your disk, make sure you are looking at the whole disk
and just a partition of it. If the disk has been broken into several partitions then of
course each will appear smaller than the disk itself. To check the size of the physical
disk as detected by the system, use the BIOS setup program or a disk utility like FDISK.
- Check in your BIOS setup program for a hard disk setting like "Translation Mode".
You are looking for a setting that you can set to something like "LBA",
"Large" or "ECHS". These are BIOS translation modes. If you cannot
find any setting like this, the chances are that your motherboard does not support BIOS
translation. If the BIOS date is from July 1994 or later, it should have
translation support for large hard disks built into your BIOS, but older ones usually do
- If your motherboard has translation support, make sure it is turned on. Most
motherboards automatically enable translation when they detect a larger hard disk, but
some BIOSes do not do this properly. It is also possible that if you put a newer disk in
place of an old one, that the old standard mode is still set in the BIOS. You will usually
want a disk larger than 504 MB to be in "LBA" mode, since this is the de facto
standard translation mode for large disks.
- If you do not have native translation support, you will have to add it to the system in
order to allow full access to the disk. There are several ways to do this, generally
involving either an upgrade to the BIOS or hardware, or the use of a software drive
overlay. This section of the Reference Guide
discusses adding translation support to a system..
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