Using the traditional ATA (IDE)
interface limits the system to a maximum drive capacity of 528 Mbytes. The cause of this
limitation is Int 13h (BIOS) and ATA (IDE) field sizes for the CHS (Cylinder, Head, and
Sector) entries.
Because the system must perform a
translation between the CHS parameters recognized by the drive and those established in
the Int 13h code, parameters are limited to the smaller of the field sizes allowed for
each parameter by the BIOS and the ATA (IDE) register set. The chart below displays the
BIOS, ATA (IDE), and limiting field size.
528-Mbyte
Limitation
| |
Int 13h BIOS |
ATA (IDE) |
Limitation |
| Maximum Sectors/Track |
63 |
255 |
63 |
| Number of heads |
255 |
16 |
16 |
| Number of Cylinders |
1,024 |
65,536 |
1,024 |
| Maximum Capacity |
8.4 Gbytes |
136.9 Gbytes |
528 Mbytes |
The maximum system drive capacity in a
combined BIOS/ATA (IDE) setup is determined by the limiting field size 528 Mbytes.
Currently, computers are being shipped with a BIOS that implements Extended Int 13h or
"Logical Block Addressing" (LBA), both of which are solutions to the 528-Mbyte
limitation.
4096 Cylinder (2.1-Gbyte) Limitation
Some computers have a BIOS that does not
properly deal with the "13th bit". The 13th bit is needed to provide support for
a drive having 4096 or more cylinders. The chart below displays the corresponding cylinder
values in decimal, hex, and binary values.
| Decimal |
|
Hex |
|
Binary |
|
Size |
| 1023 |
= |
3FF |
= |
10 bits |
= |
528 Mbytes |
| 2047 |
= |
7FF |
= |
11 bits |
= |
1.0 Gbytes |
| 4095 |
= |
FFF |
= |
12 bits |
= |
2.1 Gbytes |
| 8191 |
= |
1FFF |
= |
13 bits |
= |
4.2 Gbytes |
| 16383 |
= |
3FFF |
= |
14 bits |
= |
8.4 Gbytes |
If you have added a new drive and your
system locks right after turning the power on or when you are in the CMOS, there may be
several causes. Verify that the data cable is properly attached to your drive, pin 1 is
correct, and the cable is not off-shifted a row of pins. If your new drive is larger than
2.1 Gbytes and the CMOS is set to "AUTO", you may have a BIOS with a 4096 or
greater cylinder limitation. In this case, power off your system, remove your new drive,
and follow the instructions that DiscWizard provides. When
configuring CMOS, Do NOT use AUTO. Rather, choose one of the following:
- USER DEFINABLE set to 1024 cyls 16 hds 63
sects
or
- Drive type 1
Another option is to contact your
computer manufacturer to get a BIOS upgrade that will support more than 4096 cylinders.
6322 Cylinder (3.27-Gbyte) Limitation
Some computers have a BIOS that does not
properly handle a cylinder value over 6322. If you are in the CMOS attempting to set the
cylinder value higher than 6322 (for a 3.27 Gbyte+ drive) and your computer hangs, your
computer may have a BIOS with this limitation. To by pass the limitation, you have two
options:
Invalid BIOS Information
Some computers have a BIOS that may
display invalid information in the CMOS. This issue may show up in one of two ways:
The CMOS will display
invalid drive parameters. However, the BIOS is translating the drive correctly.
The CMOS will display the
drive parameters and capacity correctly. However, the BIOS is not translating the drive
correctly.
To ensure your drive is translated to its
full capacity, you will need to check the actual drive size. This can be done when
creating partitions on the drive.
8.4-Gbyte Limitation
If your drive is larger than 8.4 Gbytes,
the capacity may exceed the limits of your system BIOS and operating system. Most system
BIOSs cannot support ATA drives this large. DOS and Windows operating systems limit the
drive capacity to 8.4 Gbytes per physical drive and 2 Gbytes per partition. Because of
these limitations, a 32-bit file allocation table (FAT32) is required to acheive full
capacity of your drive, beyond 8.4 Gbytes. To acheive full capacity of your drive, you
will need BIOS support for drives greater than 8.4 Gbytes and a Windows operating system
that supports FAT32. This support is available by way of the following methods:
A third party device
driver, such as Disk Manager (Disk Manager is provided on the DiscWizard diskette
included with your drive)
An intelligent ATA Host
Adapter
A system BIOS upgrade
