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The manufacturers of most compatibles have enhanced the motherboard ROM BIOS tables in three ways:

•  Additional types. The first thing that the manufacturers did was add more drive types to the table. Because the table had room for 47 or more entries, many compatible BIOS versions simply filled out all the entries with values that matched the most popular drives on the market, generally making drive installations easier. IBM tables often were short of the maximum number of possible entries.
 

•  User-definable drive types. Most makers of compatibles then added a user-definable type, which used unused areas of the CMOS memory to store all the drive-parameter information. This was an excellent solution because during setup you can type a parameter that matches any drive on the market. The only drawback is that if the CMOS battery dies or the saved values are corrupted in some way, you would have to re-enter the information exactly as it was before to regain access to the drive. Many people did not write down the parameters that they used, or they used improper parameters that caused problems.
 

•  Automatic detection. Most of the newer BIOS versions include a feature that is specific to IDE drives. Because most IDE drives are intelligent and will respond to a command called Identify Drive, the BIOS sends this command to the drive, which then responds with the correct parameters. This feature eliminates the need to type the parameters because the BIOS will accept what the drive tells it.

As mentioned earlier, most of the newer compatible BIOS versions have both the user-definable type feature and automatic detection for IDE drives.

ROM Replacement

One way around the drive-table limits is to purchase and install a new ROM BIOS. A Phoenix ROM BIOS set, for example, costs about $50. These ROMs include a user-definable drive-type setting, which is the most elegant solution to this problem. A new set of ROMs probably will give you additional features, such as a built-in setup program, support for HD or ED 3 1/2-inch floppy drives, and Enhanced Keyboard support.

RLL/ESDI System Configuration

RLL and ESDI drives usually are not represented in the internal drive tables of older BIOS versions. Consequently, the controllers for these drives often have an on-board ROM BIOS that either contains an internal list of choices for the interface or enables you to dynamically configure (define) the controller to the specific geometry of the drive.

If you have a motherboard BIOS with a user-defined drive type (recommended), you can simply enter the correct parameters and the drive will be supported. (Remember to write down the parameters that you use; if you lose them, you can lose access to the drive if you don't re-enter the parameters properly.) When using a user-definable type, you can disable the controller BIOS.

IDE System Configuration

Intelligent IDE drives can use the geometry that represents their true physical parameters, or they can translate to other drive geometries that have the same number of sectors or fewer. Simply select a type, or enter a user-definable type that is less than or equal to the total capacity of the drive.

SCSI System Configuration

Almost all SCSI drives use DRIVE TYPE 0 or NONE because the host adapter BIOS and the drive communicate to establish the drive geometry. The low-level formatting routines usually are accessed on the host adapter through a configuration, setup, and format program. All SCSI drives are low-level formatted at the factory.

Formatting and Software Installation

Proper setup and formatting are critical to a drive's performance and reliability. This section describes the procedures used to format a hard disk drive correctly. Use these procedures when you install a new drive in a system or immediately after you recover data from a hard disk that has been exhibiting problems.

Three major steps complete the formatting process for a hard disk drive subsystem:

•  Low-level formatting

•  Partitioning

•  High-level formatting

Considerations Before Low-Level Formatting

In a low-level format (LLF), which is a "real" format, the tracks and sectors of the disk are outlined and written. During the LLF, data is written across the entire disk. An improper LLF results in lost data and in many read and write failures. You need to consider several things before initiating an LLF.

Data Backup

Low-level formatting is the primary standard repair procedure for hard disk drives that are having problems. Because data values are copied to the drive at every possible location during an LLF, before performing and LLF you should back up any data on the drive if you will ever need access to that data again.

Because an LLF overwrites all the data on a drive, it is a good way to erase an entire drive if you are trying to ensure that nobody will be able to get data from it.

System Temperature

Sector header and trailer information is written or updated only during the LLF operation. During normal read and write activity, only the 512 bytes plus the Cyclic Redundancy Check (CRC) bytes in the trailer are written in a sector. Temperature-induced dimensional changes in the drive platters during read and write operations are not a problem with modern voice-coil actuators used today. However, it is still doesn't hurt to leave the system's power on for at least 30 minutes before performing an LLF on its hard disk. This step ensures that the platters are at a normal operating temperature.

Drive Operating Position

Another consideration before formatting a drive is ensuring that the drive is formatted in the operating position it will have when it is installed in the system. Gravity can place on the head actuator different loads that can cause mistracking if the drive changes between a vertical and a horizontal position. This effect is minimized or even eliminated in most voice-coil drives, but this procedure cannot hurt.

Additionally, drives that are not properly shock-mounted should be formatted only when they are installed in the system because the installation screws exert twisting forces on the drive's Head Disk Assembly (HDA), which can cause mistracking. If you format the drive with the mounting screws installed tightly, it may not read with the screws out, and vice versa. Be careful not to overtighten the mounting screws because doing so can stress the HDA. This usually is not a problem if the drive's HDA is isolated from the frame by rubber bushings.