The Source  for Mac Performance News and Reviews

Q:  Most All IDE Drives Sold Now are ATA/100 or higher rated - are they Compatible with older IDE/ATA Interfaces?

A:  Most all drives made in the last year are ATA/100 rated. (Some ATA/133 drives are starting to appear in mid-late 2001 also, such as Maxtor's very large drives up to 160GB - but see the note below on issues with IDE drives larger than 128GB.) Like ATA/66, ATA/33, etc. - the ATA/100 specification is designed to be backward compatible (note all the ATA/100 drive reports in the Drive Compatibility Database here from even ATA/3 onboard IDE Beige G3s, and even some older macs like the 6500, Starmax clones, etc.)

However just like putting PC133 ram in a 100mhz bus system won't make the memory run at 133mhz, a drive with an ATA/100 rating can't make the older onboard interface run at ATA/100 speeds. The IDE controller chip has that limit. However the modern IDE drives will show better performance than the original older drives, since most older original equipment drives were not as fast as even the older IDE interfaces. This is shown in my 1998 Beige G3 HD upgrade guide performance tests page - even with ATA/3 (16.6MB/sec max), a 1998 maxtor drive was significantly faster than the original drive the system shipped with.

Although the issue of backward compatibility has been noted in many articles, news posts and literally thousands of drive database posts for years now at the man site, I'm posting this here also as a FYI for those that seem concerned or confused about putting an ATA/100 drive (like most every drive is now) in a Mac with a slower rated interface.

The main www.xlr8yourmac.com IDE articles page has links to guides I've done on upgrading/adding IDE drives in a Beige G3 Minitower, B&W G3 rev 2/G4 AGP Mac (adding 2nd drive) as well as PowerBooks (from Wallstreet to PB G3 2000 to PB G4).

If you have a B&W G3 (Blue and White G3) that does not have the dual drive cable and stacked drive bracket, check the IDE chip marking as the early model IDE chip models can have data corruption problems as noted in this B&W G3 rev 1 article and in many drive database reports since then.
If your B&W G3 doesn't have the dual drive cable and stacked bracket, be sure to check the IDE chip marking on the motherboard to see if it matches the marking shown in my B&W rev 2 features page. If it doesn't , I'd suggest adding a Mac PCI IDE card for use with any modern replacement drive.

Notes on Drives larger than 128GB Maxtor was the first vendor to release an IDE drive larger than 128GB, such as their 160GB ATA/133 model. As noted in past drive database reports and main site news items, an ATA/133 compatible interface is required to be able to use the full capacity of the drive. (If used with an ATA/3, ATA/33, ATA/66, etc. card the drive max size is limited to 128GB or so.)

If you own an Acard ATA/100+ Mac IDE PCI Card, there is an update that is reported to allow full use of the >128GB drives. (This chip is ATA/133 compatible). A reader noted in a Jan 2002 drive database entry for his Maxtor 160GB drive that the Acard OS X driver update for this Acard ATA/100+ card allowed full use of the 160GB drive. (See the Jan 4th, 2002 news page for details.)

(FYI - Readers have reported the SIIG ATA/100+ and Miglia ATA/100+ Mac IDE cards are really based on the same Acard controller, so this tip may also work for those card owners.)