PC Hardware

Breaking the 8.4-GB barrier

Hard disk drives larger than 8.4 GB require a BIOS that supports enhanced interrupt 13h extensions for very large drives. Which method is used will depend on the system's age, operating system, and the drive in question. Newer machines come with built-in support in the system BIOS. There are three methods you can use to enable this function on older PCs that do not come with native support:

  • Upgrade the system BIOS.

  • Install a hard disk drive adapter with Int 13h support.

  • Use a software program from the drive maker to allow the system to access the drive.

Depending on the system BIOS, you might not be able to display the entire size of the drive while in BIOS/CMOS Setup. Check the manual for the BIOS and operating environment for more details.

While the procedures just described will let the system recognize the drive, the maximum partition size will still be determined by the operating system in question. Be sure to check the procedures for the version you will be using with any third-party software. Newer versions of Windows (98, NT, and 2000) allow very large partitions.

If you use an older FDISK to prepare the drive, you will not be able to use the entire contents as a single volume. If you use Microsoft's FAT12- or FAT16-based FDISK, the largest single partition will still be 2.1 GB unless a third-party partitioning program is used. New versions of Windows can access partitions greater than 2.1GB, but if you plan to use a dual-boot configuration, be sure that any partition is compatible with the operating system you want to use to view the files it contains. NTFS and FAT32 partitions are not visible to older versions of Windows, MS-DOS, or UNIX.

Ultra DMA

While questions about the latest incarnation of ATA/DMA drives are not likely to appear on the current A+ Exam, a good computer technician should be conversant with them and expect to see them as part of the certification renewal process. Ultra DMA/33 is a faster drive technology that can be used on virtually any Pentium motherboard. Ultra DMA/66 offers raw data transfers at twice the speed of its DMA/33 older sibling. It requires a compatible system bus on the motherboard (or a special controller card), BIOS, and special IDE cable certified for that speed. They are easy to identify. One 40-pin connector is blue, the other black. Most are also labeled for Ultra DMA/66.