Page 1
(Part 1)
SCSI vs. IDE Bus Mastering for DAWs
by D. Glen Cardenas and Jose M. Catena 1999/2000

  Table of Contents (click on heading for direct link) Page       Page
Part 1 Introduction 1     Bus Mastering and DMA 7
  A Question of Drives 1     Enabling UDMA Bus Mastering 8
  The Contenders 1   Part 4 Comparing Drives 9
  Other Considerations 2     Media Access Speed 9
Part 2 About SCSI 3     Interface Access Speed 15
  The History of SCSI 3     Cost 15
  The SCSI Standard 3   Part 5 DAW Considerations 17
  Setting Up SCSI 4     DAW Disk Benchmark 17
Part 3 About IDE 5     CPU Power Bottleneck 18
  The History of IDE 5     Conclusions 19
  Bus Mastering 5, 6   Part 6 Notes: References 20
          Credits 20


Look in any newsgroup devoted to DAW discussion and sooner or later there will be some sort of mention regarding favorite hard disks or preferred disk formatting techniques or optimum parameter settings or SOMETHING about the impact of specific hard drives on the performance of audio streaming. Often, the argument starts with the personal preference between SCSI and IDE disk drives. Why "personal preference"? We think that after going over the data in this article, you will see that there's a lot of room for subjective opinion in this discussion. Far from proving that there is one clear winner between the two, research has proven just the opposite. There is a lot to be said for SCSI. On the other hand, many readers are about to say "A-HA! I knew SCSI was better!" and are about to be disappointed. This will come as a shock to many hard core SCSI advocates - perhaps even an insult! However, before proponents on either side start sending us an HTML flame-thrower, look over the data here and keep an open mind. You, too, may discover things about both formats you didn't know and even more chilling, things about the whole argument that you never took into account before.

One contention with this whole argument has been a blatant lack of fact and information in the discussions seen in many news groups. This article is out to change this by offering a full range of facts, specifications and information from manufacturers, testers and hackers. The facts as we have found them show that either format will work very well in any system, and that one format can have a slight edge over the other if properly set up and under some conditions. This may seem like overkill for a discussion that is destined to be a washout (so to speak), so why bother? Well, even though there may be little advantage to either EIDE or SCSI in most system configurations, there are very important specifications to examine in terms of the drives themselves, and in cases where the format DOES make a difference, it is good to have those facts and a clear understanding of them. Besides, we don't want to offer conclusions without backing them up or it would be just more opinion and nothing else. No thanks. This may be about to rock some people's boats and it should have something to stand on. In the following pages we offer a fair sample of the information gleaned during the past few weeks and over the past several years of looking at this issue. The information is formatted in a way that, hopefully, will provide the reader with a strong overview of all aspects of the issue and any conclusions. Information is power. Have some juice!

A Question of Drives
The heart of any successful DAW, be it a PC, Mac, Amiga or whatever, is the storage media. In this case, the hard disk drive. No matter how sophisticated the software or how clean the sound card, it boils down to the data stored on the disk. If you can't get the data off the drive in a timely manor, well then, what's the point.

Although there are many who use the Mac for their DAW, and there is now a renewed interest in the Amiga as well, we will limit this discussion to the PC, and further more, to the 32 bit Windows based PC. This isn't to say that Windows is a better platform than the BeOS, Linux or a number of other alternative operating systems. In fact, it's probably the worst! However, it's just a practical fact that it's the most popular and thus the most widely supported. When we talk about Windows in this article, we will be referring to Windows 95B, Windows 98, and Windows NT4. Each version has some specific considerations and when these become relevant, a clear distinction between them will be made.

The Contenders
There are two major types of disk drive formats associated with personal computers in general, IDE and SCSI. The IDE system is built into all modern mother boards and is the default choice for almost all PC users. The SCSI system is supported directly on some newer mother boards but by and large, requires a separate PCI controller card called a "host adapter" to which all SCSI devices are connected.

Go to Page 2 (Part 2); Back to TOC