HARD DRIVES

A hard drive is the archive or library of your computer; it's the place where information is permanently stored. The name 'hard drive' came about as a wordplay on floppy drive. They both store data in basically the same way; a read/write head moves back and forth across the surface of a spinning disk that is coated with a surface that is sensitive to magnetism and writes by creating a magnetized spot on the disk or reads by sensing whether that spot is magnetized or not. The floppy disk came first and worked so well that high speed solid metal disks enclosed in a sealed chamber were used to design the first hard disks. Because hard disk platters are in a controlled environment (an airless sealed chamber), the heads can be much closer to the surface of the disks, the disks can spin much faster and control can be much more precise. That allows much more data to be packed into the same space and why hard disks can store so much more information than any floppy disk.

As you might imagine, the first hard drives were slow, bulky, had limited storage space and were very expensive. Those factors caused the first IBM-PC to be equipped only with floppy drives - a hard drive was not an option. The first hard drives offered for the PCs were 5 to 10 Mb in size and cost a fortune. As more and more PCs reached the market and the demand for storage continued to rise, the manufacturers caught up with the demand. 40 Mb drives were soon the standard on the basic (second generation) IBM-PCs and drives as large as 100 Mb were being offered. Now hard drives are commonplace - they are fast, small, cheap, extremely well built and can hold a tremendous amount of data. One of the examples I've read about compares a 5.25" 10 Mb drive offered in 1982 at a cost of $1,500 to a 3.25" 20Gb drive today at a cost of less than $150. 2,000 times the storage capacity at 1/10th the cost!

The hard drives are installed in 'bays' in the case and connected to the mainboard through the IDE (Integrated Drive Electronics) interface by the use of a flat 40 pin cable. Most mainboards have the IDE interface built-in and have two IDE connectors on the mainboard. The two connectors are labeled IDE-1 and IDE-2 and you may connect up to two drives to each connector - a master drive and a slave. Your main drive (drive C) must always be connected to IDE-1, and be the master if you have two drives. The Slave/Master status of a drive is determined by jumpers on the drive. All drives have the jumpers and they are all different, so I can't tell you how to set them - but the instructions are usually on the drive.

A word of caution: when two drives are connected to the same IDE connector, data will be transfered to and from the mainboard only at the speed of the slowest drive. In the real world that means that if you have a CD-ROM drive in your computer it should be connected (via its own cable) to IDE-2, not as the slave on IDE-1, because a CD-ROM drive transfers data MUCH slower than a hard disk. Even slower is a SuperDisk or ZIP drive - that would REALLY bog your data transfer down! Slowest yet would be a back-up tape unit. Most of the time this is not a problem but it is something to keep in mind if you are considering adding drives to your computer.

A way around the limitations imposed by the IDE interface is to install a SCSI interface (see the section on SCSI). By adding SCSI, you may keep only your fastest drive on IDE-1 and add all slower drives as SCSI drives. You must plan ahead as SCSI drives and IDE drives are built differently - IDE uses a 40 pin cable, SCSI a 50 pin cable, for instance - and SCSI drives are usually more expensive, but you may add up to 6 additional drives by using SCSI and they don't have to be in the same case with your mainboard.

Another way around some of the IDE limitations is to add some of the slowest drives through your parallel (printer) port. I've seen some SuperDisk and ZIP drives offered with that option and I believe some back-up tape units and cartridge hard drive units are offered that way as well. At any rate, it's another option a person could explore.

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