ATA 133 is only Maxtor. I believe IBM and Intel have already rejected it, since most drives never get over the 66mb spec. Most of all it is because of the PCI bus itself and spindle speed, even 64bit PCI can't sustain IDE 100mb. I have a 5400rpm ATA 100, and my 7200 rpm ATA 66 beats it, barely. I do a have a 7200rpm ATA 100 drive that flies, and can get over 66mb mark on my Promise controller, but when running apps, doing large disk transfers, playing games, compiling, encoding, I don't notice the difference. I did notice going from ATA 33 to ATA 66, but not much since. My next machine after the 2nd gen P4's come out will just have SCSI.