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Microphone Month 3

SCSI versus IDE/DMA in DAW systems, Part 2

Today we will continue with our SCSI/ATA question from yesterday by focusing more on ATA issues, and how they apply to a modern DAW. If you haven’t already read yesterday’s tip we recommend you start there.

Right now modern ATA architecture only supports four devices (hard drive, CDR, etc.). In a DAW-based personal studio, you could feasibly work with an ATA (UDMA 33 or 66) hard disk setup, provided your HD audio storage needs weren’t going to increase dramatically. This infers that you might want to have some method other than hard disk to backup and archive your audio data, be it CDR, DAT, Jaz, etc. If your needs expand a lot you can always swap out existing ATA drives for larger ones or you could go ahead and acquire a SCSI (or FireWire when it becomes better supported) card and HD as your storage needs increase in the future.

Originally most Macs came factory-equipped with internal SCSI drives and a SCSI peripheral port, however now both PCs and Macs use ATA 33 & 66 drives as standard equipment. In the newest Macs all traces of SCSI are gone. This is primarily because these fast IDE drives and associated peripherals are much less expensive. Although SCSI drives can achieve higher throughput, a single ATA drive on its own bus can perform at levels that realistically compete with SCSI and make the ATA drive a worthwhile choice for most applications, including audio – provided your audio drive is dedicated to that task alone. Digital audio involves the transfer of large files, written sequentially on the hard drive, if the drive is not dedicated to audio, interruptions can occur causing glitches in your recordings. Having a dedicated drive will also reduce fragmentation that could cause performance issues. Yes, you “can” record your audio on your main hard drive, or even make a unique partition for it, but we do not recommend it. Real world experience has shown us a separate drive is best, for many reasons we don’t have space to get into.

Consider how many IDE/ATA devices are already in use by your computer. When you put an ATA device on a buss with another one both devices’ performance can suffer slightly. If you’ve got an ATA/33 or ATA/66 hard drive, regular ATA CD-ROM, and an ATA CD-RW, zip or jaz drive, that only leaves room on your 2 IDE busses [primary and secondary; two devices per buss] for one more device. At this point your bandwidth can get pretty tight because of the demands put on the IDE busses and CPU. Some of the processing of data for ATA is done by your computer’s CPU (the addition of UDMA to the ATA standard remedied a lot of this), whereas SCSI controllers have dedicated processors, which helps them keep data moving even if the computer is getting bogged down with other tasks. If you’re working on multimedia (audio and video/graphical content) or multitrack 24/96 audio, this difference is where you can begin to show performance hiccups. Furthermore, IDE devices can only be addressed one at a time, meaning that if one gets a command, it’s going to execute that command until it is complete, whereas with SCSI multiple devices can execute commands from a queue and work concurrently.

Taking all of this into consideration, an excellent ATA home computer drive setup can still be had. It would consist of one internal System drive for the operating system, applications and other files, one internal dedicated Audio drive with a rotational speed of at least 7200 rpm and enough storage to fulfill your current needs [on its own buss], and a CD-RW for archival/backup requirements. If you don’t have any means of backup (we’ll assume that’s just a temporary condition) you should definitely invest in more hard drive space (larger drives), although it is HIGHLY preferable to have the ability to backup your files often – and not just to another hard drive (though that’s better than nothing).

This has just been an overview of some of the issues. We intentionally have not talked about concrete performance measurements like “track count” because we find they aren’t all that concrete. There’s always a pretty big difference between what is theoretically possible and what actually ends up happening in practice. There is much more to it all, but you don’t need to try to learn everything because chances are only bits and pieces of the overall picture really apply to you. The problem is knowing which pieces are pertinent to your specific concerns. That is where we can help. If you really want to be an expert the information and resources are out there to do that. If you want to make music, call us.

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, 5/3/99, 8/25/98, and 9/11/97, or search the inSync archives for all references.

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