Build A PC

A custom PC configuration guide. © 2000,2001,2002 by Jef Poskanzer.


The big choice here is between EIDE and SCSI. The interface speeds look like this:

Disk Interface Speeds
Ultra-320 SCSI320 MB/sec
Serial ATA187 MB/sec
Ultra-160 SCSI160 MB/sec
ATA/133133 MB/sec
ATA/100100 MB/sec
Ultra-2 Wide SCSI80 MB/sec
ATA/6666 MB/sec
Ultra Wide SCSI40 MB/sec
ATA/3333 MB/sec

The interface speeds are comparable, with SCSI being generally faster, but those speeds are kind of theoretical. The speed that a disk can actually transfer bytes on a sustained basis is lower, maybe 45 MB/sec for current disks. Also, some chipsets have problems with high transfer rates too.

Besides, is ultimate disk speed even that important? If your system has enough memory, you don't need real fast disk access. Furthermore, there are the mechanical issues - heat, noise, and reliability. I actually prefer disks that spin slower, because in general they run cooler and quieter and I think that makes them less likely to fail. While the current standard seems to be 7200 RPM and you can get high-end disks that spin at 10000 RPM or even faster, I prefer 5400 RPM disks from a year or so ago. Given that, the latest ultra-high-speed interfaces are not necessary - for 5400 RPM disks, anything faster than ATA/33 is overkill. And actually, if you look at the specs for 7200 RPM disks, you'll find that their maximum sustained transfer rates either fit into or barely exceed ATA/33.

So if the interface speed isn't actually that important, we're left with price, and prices on EIDE disks are much lower than the equivalent SCSI drives, typically by a factor of two or three. Personally, I think SCSI is on the way out. The only place it has a clear advantage is if you want to put multiple disks on one system, and that's just not a very large market segment.

You can read a whole lot more about EIDE vs. SCSI at

The best hard disks are made by:

Also, on the issue of speed vs. reliability, there's some indication that the market is actually splitting into two segments along these lines. While most new disks are still pushing the high end of rotational speed, going to 10,000 or even 15,000 RPM, there are a few that are going the opposite direction. For instance, take a look at the Maxtor DiamondMax 60, reviewed at This is a fairly recent drive, with 60GB and ATA/66, but it spins at only 5400 RPM. Instead of going for the fastest possible speed, the designers optimized for low noise instead. That's good by itself, but it also translates to less heat and vibration and therefore to better reliability. But if you absolutely must have 7200 RPM, there's the DiamondMax Plus 60, which also has the faster ATA/100 interface speed.

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