Properly named Ultra ATA 100, and sometimes refered to as UDMA 100. An incremental improvement over ATA 33 and ATA 66, which are in turn updated versions of the IDE drive bus, which can theoretically support data transfer at 100 MB/s. Other than simply being faster than previous incarnations, the main difference between it and the original IDE spec is that the 80 pin cables used for ATA 66 are now required, instead of the older 40 pin ones.