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SCSI versus IDE/DMA in DAW systems, Part 1

The answer to today’s question is deep enough that it could occupy an entire week’s worth of inSync. In the interest of our mutual sanity, we’re going to limit the answer to two days’ worth. Part 1 is today. Part 2 will be tomorrow.

“I recently read an article in an audio mag that said that IDE technology has advanced now to the point that SCSI could become ‘passe.’ Given the advancements in IDE performance for HD’s as of late, which is best, IDE or SCSI, for HD recording and why? What are the advancements that are significant in IDE drives? Which format is better for CD-RW’s?”

The quickest and absolutely most accurate answer to this question is, “It depends.” That’s the fact. As much as we all hate reading articles that don’t give us a clear-cut good versus evil answer, the reality is it just depends on a number of things. I’ve been reading a lot of articles on line lately that go into nauseating detail about all the voltages, speeds, specs, exceptions and other minutiae of computers and hard drives. Many of these are quite good, offering well researched accurate information. But what does all the information mean? Unless you really have a LOT of time to truly become an expert on the subject yourself, you are still going to ultimately be taking a recommendation from someone, no matter how cloaked it is in objective “facts.” Any information given can be dangerous because there are so many variables governing real world performance that people just don’t know how much they don’t know. Many people read these articles and walk away assuming they are now an expert on the subject when really all they’ve done is capture about 20% of the most pertinent information that happened to make sense against what they already knew (this is normal, we all do it). And the bottom line is they probably only garnered a few “conclusions” that were made by the author, not the raw data and understanding required to draw their own conclusions as measured against grounded assessments of what is going to be most important to them.

This is one major reason why time and time again we recommend you speak to your Sweetwater Sales Engineer. Not because they are the world’s foremost authorities on the subject – they know their stuff, but let’s be realistic – it’s because we build and install thousands of systems a year. After doing it for a while you just learn what works well and what doesn’t. It’s miles beyond reading specs and promises on paper. We’re in it at a practical level with our customers. You can take advantage of that experience. When we sell a system, it better work, or we’ll be jumping through some hoops to make it work, and then we learn for next time.

Now, with all of that said, we will now try to offer a few general points that you should take to heart. Along the way I am going to state some subjective opinions about things based solely on what we’ve seen and the tech support we’ve done. We don’t have the space to give you the raw data, but the conclusions we arrive at are based on the experiences we’ve had (which are many). While some of our more opinionated readers may disagree with some things, their experiences are still not our experiences, and we’re the ones with the column. So there!

Part 1

Remember, it always depends. Please read everything here with the understanding that there are many exceptions.

A quick note: the terms IDE and ATA are interchangeable when referring to modern storage devices of this type, with ATA actually being preferred. This is because all IDE drives made now conform to the ATA specification; in this sense ATA refers to an IDE storage device manufactured since the ATA specification became standard.

Overall our experience continues to reinforce the idea that, all other things being equal, SCSI is better… and this applies to all drives, be it hard disk or CD-RW. The availability to connect more devices in a chain, generally higher quality equipment and typically higher data transfer rates (in practice) with less work from the CPU make SCSI drives an automatic choice in many professionally-configured DAW systems. This isn’t to say that ATA drives aren’t capable of producing professional-quality audio, it just means that you’re still more likely to reach the limitations of ATA faster than you are SCSI, especially since the advent of 24/96 audio. Another advantage SCSI has over ATA is portability – it’s nice to know that if you need to take your tracks to another location for editing or mastering that you can literally carry an external SCSI device to another studio and easily hook it up to another familiar (same type) computer. Of course the catch with all of this is, as always, that all other things are not equal… most notably the price in this case. SCSI hardware is significantly more expensive than ATA hardware. When one starts to examine current performance differences against the price tag, SCSI becomes harder to justify, but in many cases it is still the way to go. It just “depends” on what you are actually going to be doing and what the other components of the system are. Obviously anyone currently looking at mid- to high-end systems like Pro Tools knows they are going to be using SCSI. There are other advantages to ATA technology, but much of it beyond the scope of what we can realistically cover in this format.

One other caveat here is that SCSI, as a principle technology, is most definitely on the decline. ATA, firewire, USB, and other formats are all right on its heels and gaining. Two or three years from now you are going to see far fewer systems relying on SCSI as the other technologies continue to rapidly improve. The same reader who asked the above questions also relayed doubt about SCSI based on numerous past Tech Tips of ours relating to problems with SCSI. SCSI does have its share of problems, but many of them are brought on by people using it in ways it was not intended to be used. Of course anything that is in widespread use is also likely to have more “problems” than something fewer people use, especially when it can be used in so many different ways. In that sense it’s just simple statistics. All things considered, SCSI is actually a very reliable and robust format so long as you stay well within its operating parameters.

You must also keep in mind there are many different forms of SCSI with vastly different performance characteristics. Just a few variants are Ultra SCSI, Ultra2 SCSI, Ultra Wide SCSI, and Ultra2Wide SCSI. Which one might be best for your needs will vary, but right now the most popular protocol for audio recording is Ultra Wide SCSI. Ultra2Wide, which is theoretically twice as fast, may become more popular in the future as computer bus speeds improve enough to fully utilize it in audio systems.

Recent ATA advancements don’t center on the drives so much as the motherboards’ ability to utilize them at their rated data transfer capabilities. The difference between ATA/33 and ATA/66 (also known as UDMA/33 or UDMA/66) is the transfer of megabytes per second (MB/s). Theoretically, an ATA/33 can transfer 33MB/s, and an ATA/66 transfers 66MB/s. By way of comparison Ultra Wide SCSI sports 40MB/s and Ultra2Wide SCSI sports 80 MB/s, but don’t let the specs mislead you. There’s much more to this than raw speed specifications.

Although ATA/66 drives have been around for a couple of years now, motherboards with IDE busses that could support that rate of transfer are only relatively recently available. There are now ATA100 drives in development – which means motherboards will eventually have to be made/updated to support them as well. Give it a few months before you start seeing these new drives in abundance, although even at that point SCSI drives will probably remain atop the audio/video roost for the time being.

That’s all for today. We’ll devote tomorrow’s part 2 to a few more practical aspects of using ATA drives with your DAW.

For more in-depth information feel free to probe a few of our past tips on SCSI and ATA drive issues. You can start with the tips from 6/2/2000,

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Being music makers ourselves, we love geeking out on all things gear. From the tweakiest techniques to the biggest ideas, our experts work hard to constantly supply inSync with a steady stream of helpful, in-depth demos, reviews, how-tos, news, and interviews. With over 28,000 articles and counting, inSync is your FREE resource for breaking news, reviews, demos, interviews, and more.

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