This item is from the Yet Another Enhanced IDE/Fast-ATA/ATA-2 FAQ, by John Wehman and Peter den Haan with numerous contributions by others. (v1.92).
To everything EIDE has on offer, Ultra-ATA adds the following:
o Even faster transfer modes, most importantly DMA/33 with double the bandwidth of DMA mode 2 and PIO mode 4. There are no new PIO modes.
o Improved reliability using DMA/16 and DMA/33. A checksum is added to the data sent over the ATA interface. That way, data corruption can be detected and the data retransmitted. On an ordinary EIDE interface you wouldn't notice the corruption until it was too late.
Ultra-ATA was first proposed by Quantum and is widely accepted now.