OS/2 e-Zine! - The Need for Speed

The Need for Speed - by Jon Cochran

A Tale of Two Buses

Throughout the ages, one question has plagued man, that being "What is the meaning of life?" More recently, a similar question has plagued the realm of computer users, it being "SCSI or IDE?" Chances are, if you're debating that question, you're either planning a massive upgrade, or building an entirely new computer. Why's that, you ask? We'll get into that later.

IDE and SCSI are two different bus architectures used to communicate with storage devices. IDE (which stands for Integrated Drive Electronics) is by far the oldest of the two sometimes being older than that teenager who shows you how to use your computer.

IDE, being as old as it, suffers from many limitations. First of all, IDE can't support more than two devices, and for the most part, those devices can only be hard drives (although there are ways around this). Second, IDE is not designed for a multitasking environment, and can't support more than one disk I/O request at a time. Third, IDE is just plain slow. Even hoping for the best, IDE would probably top out at around 2MB/Sec. Fourth, and most crippling, IDE can't support devices over 528MB (1024 cylinders) in size.

In 1995, EIDE made its debut on the scene. Of all the refinements in EIDE (Enhanced IDE), the biggest improvement was support for hard drives over 528MB. Second, a variety of devices (notably CD-ROMs and tape drives) were now supported. Third, multiple I/O requests were supported by the EIDE standard. And EIDE was faster than regular IDE as well. Some EIDE adapters rate themselves as having a transfer rate of 14MB/sec, but only in a "burst mode", which means, it can only obtain that speed after it "revs up".

On the other side of the ring stands SCSI (Small Computer Standard Interface). SCSI was, and is, everything that IDE is not. Originally SCSI could support roughly 7 devices on a single adapter, but that number has since increased. The Original SCSI bus could transfer roughly 5MB/Sec. A later improvement, FAST SCSI allowed for around 10MB/sec. Even later, Fast & Wide SCSI appeared, and it had roughly double the speed of FAST SCSI (but it required a different cabling system). SCSI also supports multiple I/O requests, which makes it ideal for multitasking systems (it's more robust in this area than EIDE is).

With all the advantages SCSI seemingly enjoys, you may wonder why it hasn't taken the computer world by storm. One simple reason: price. SCSI was (and still is) more expensive than IDE. With the advent of EIDE, the advantages of SCSI narrowed, and its main calling became heavy duty server applications. A simple EIDE interface can usually be bought for about $30. A simple SCSI interface will cost roughly double that. A SCSI CD-ROM is also much more expensive than its IDE counterpart, ditto for a SCSI hard drive. When you add everything up, you may end up spending a couple hundred dollars more than you intended.

EIDE is, and will remain for some time to come, the dominant standard for personal computers. Almost any computer you buy off the shelf has an EIDE adapter built into the motherboard. With this kind of proliferation, the standard is hard to avoid.

If you're planning a new computer, the decision is a simple economic one. If you want the extra performance, and are comfortable paying for it, do it. If you're buying an off the shelf computer, you're probably going to be stuck with EIDE.

Will you notice a big difference, or any difference? For most people the answer is, "probably not." But now that you know your machine could be just that much faster, don't you want to start flipping through back page ads of SCSI peripherals and dream?

Jon Cochran is a full time student at Rider University majoring in History/Secondary Education. He hopes (or at least his parents do) to graduate soon.

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