At around the same time that Western Digital began promoting Enhanced IDE, Seagate
Technology created its own unofficial extension to the original AT
Attachment standard. Like Western Digital, they wanted to improve the performance of
newer hard drives; they also didn't want to wait for the next official standard. And they
certainly weren't going to just follow Western Digital! So they created a new
"standard" that they called Fast ATA. Quantum joined Seagate in
supporting this program. Later, Fast ATA-2 was created, adding more functionality
to Fast ATA.
While at the time Western Digital got the lion's share of the criticism for its Enhanced IDE program, these two terms fare only a bit better in
the confusion department. The term "Fast" is meant to connote that the interface
runs at higher speed than regular ATA; which it did. The names are confusing, however,
because they make it sound like Fast ATA-2 is related to ATA-2, and Fast ATA is related to
regular ATA. This is not so, as both are really subsets of ATA-2,
including the higher speed transfer modes and some of the other features of the official
standard. Specifically, Fast ATA includes PIO mode 3 and multiword DMA mode 1. Fast ATA-2
includes PIO modes 3 and 4, and multiword DMA modes 1 and 2.
I will give Quantum and Seagate credit for one thing: they at least stopped using these
confusing terms in the late 1990s, while Western Digital keeps painting fresh bulls-eyes
around the term "EIDE". ;^) As the IDE/ATA interface evolved, these
"Fast" terms were eventually dropped, in favor of terms like "Ultra
ATA" (which are still not technically correct, but at least are universally used in
the industry).
Unfortunately, the "Fast" business persists in some places; I recently saw a
datasheet for a Maxtor drive that claimed it was "Fast ATA-4 compatible". I have
no idea what in the blazes "Fast ATA-4" is supposed to be, but the same spec
sheet says that drive is capable of Ultra DMA/66 transfers. That's Ultra DMA mode 4, which
was defined in the ATA/ATAPI-5 standard, not ATA/ATAPI-4. Perhaps this odd "Fast ATA-4" term was
supposed to mean that the drive was using the newer DMA mode that was anticipated to make
the ATA/ATAPI-5 standard, and therefore was faster than ATA-4? Argh, these marketing
people drive me crazy sometimes. 
Next: Ultra ATA (Ultra ATA/33)
