(Advanced Technology) is the bus used in the IBM AT and compatibles (Advanced Technology) is the bus used in the IBM AT and compatibles.
by David Sears
If you want to upgrade your PC, the first thing to consider is a faster, larger hard disk. To make shopping for your dream disk easier, we've compiled a list of more than 150 hard disks of 100MB or more, complete with their specifications and the address and telephone number of each manufacturer.
Use this list as a starting point to find the disks with the specs you want in the price range you can afford. While some of these drives aren't yet widely available to consumers, they do exist; shop around. The prices listed here are mail-order prices, and they may have dropped since press time.
How to Read the Chart
The drives in this chart are listed in alphabetical order by manufacturer (you'll find addresses and telephone numbers at the end of the chart). Each manufacturer's drives are then listed by capacity--the most important specification for most people.
Following capacity, you'll find the model number, the form factor (which is the diameter of the drive's disks), the exterior dimensions of the drive (so you can make sure it fits in the space you have), and the number of heads.
Next is the most important column in the chart after capacity: seek time. Seek time is a measure of a hard disk's speed, with smaller numbers meaning a faster disk. Just two years ago, 65 milli-seconds was standard, but just look at the seek times for these drives. Most are less than 25ms, and some are considerably less than that.
The next column lists interface, which determines many of the drive's qualities (especially its speed and capacity) and the way the drive connects to your PC. Here's a brief explanation of each interface type.
AT (Advanced Technology) is the bus used in the IBM AT and compatibles. Drives designated with an AT by the manufacturer usually employ an IDE interface.
ESDI (Enhanced Small Device Interface) is an interface standard that puts some controller functions on the drive itself. ESDI allows for data transfers of 1MB-3MB per second and can be used for drives up to one gigabyte in size.
IDE (Integrated Drive Electronics), like SCSI (see below), is an interface design that puts the controller on the drive itself. IDE, however, offers lower performance.
MCA (MicroChannel Architecture) drives require a PS/2-style bus connection.
SCSI (Small Computer System Interface) is an interface standard that puts most of the controller functions on the drive itself. It offers transfer speeds of 1MB-4MB per second. SCSI also allows as many as seven additional devices to be daisychained. SCSI-2 is faster than SCSI but is fully compatible with the earlier standard.
The next column, Encoding, refers to the way data is stored on a disk. Almost all of the high-capacity drives listed here use RLL, for Run Length Limited, a system borrowed from the mainframe world that increases storage by 50-100 percent over previous encoding methods.
Under MTBF (Mean Time Between Failures), the numbers represent the hours of service you can expect from your drive. For most of these drives, the MTBF is 50,000 hours or more, which means that if you left your drive on 24 hours a day, it would last nearly six years. Most of us will be looking at 100-gigabyte drives by that time.
The last column lists price, and as mentioned above, these are mail-order prices, which may have dropped since press time.
Any column with n/a indicates that the information was not available at press time.