It is not that important. Before Western Digital's Raptor came out, the fastest IDE disks were Western Digital Speical Edition disks. They are all ATA100. Maxtor's ATA133 disks were no match due to less cache and higher seek time. WDSE disks have 8MB cache with seek time of 8.9ms, Maxtor ATA133 disks have only 2MB cache with 9ms ~ 10ms seek time.
Raptors are faster mostly due to their seek time is only 5.2ms.