PC Hardware

Other Settings

There are several other drive settings that are not necessarily limited to EIDE, but are generally associated with these larger hard disk drives.

Multiple Block Reads

The ATA standard requires each drive to activate its IRQ (see Tutorial 10, "Expansion Buses," for details of IRQ) every time it sends one sector of data. This process helps to verify good data transmission, but it slows down the computer. Multiple block reads speed up the process by reading several sectors of data at a time.

Many BIOS chips have multiple block read as an advanced feature. Enabling multiple block read can be done with third-party utilities as well. Multiple block read can also be installed using a device driver that comes with a hard disk drive controller. Always use multiple block read, if possible.

32-Bit Access

Providing 32-bit disk access is a major speed improvement over MS-DOS for the Windows 3.x and Windows for Workgroups 3.11 environments. Every time an operation is performed under Windows, Windows must use the BIOS routines to access the hard disk drive. To do this, it creates a virtual MS-DOS world, a "bubble" of conventional memory that looks and runs just as if the machine were running MS-DOS.

Enabling 32-bit file access allows Windows 3.x to talk directly to the ROM BIOS, using a protected-mode driver called VFAT.386 (found in the Windows\System directory). VFAT.386 is loaded using the [386Enh] section of the SYSTEM.INI file. With the 32-bit file loaded, Windows does not have to create an MS-DOS "bubble" to talk to the hard disk drive.

For 32-bit file access to work in older versions of Windows:

  1. Enter the line
  2.  device=c:\windows\ifshlp.sys

    into your CONFIG.SYS file. This loads the 32-bit file access driver.

  3. In the SYSTEM.INI file, add two lines to the [386enh] section:
  4.  device=vfat.386

(These protected-mode drivers replace MS-DOS FAT functions and SMARTDRV.EXE functions.)

Windows 95 and later versions of that operating system automatically install a 32-bit file access driver. 32-bit file access is transparent to EIDE and requires no special settings.

There are some other potential problems with Windows 3.x and large drives. Windows 3.x uses a file called *WDCTRL for 32-bit disk access. This file is enabled from the SYSTEM.INI [386enh] section. This driver predates LBA and will generate the error: "32 file access validation failed." If this happens, *WDCTRL needs to be updated. Most EIDE controllers and all drives now come from the factory with a disk of software. If not, look up the Web site of the hard disk drive manufacturer and download the driver.

Whenever possible, check the CMOS, look for a 32-bit disk access option, and enable it.