This version of the ATA standard was approved in early 2000 and builds on ATA-4. The major additions in the standard include the following:

• Ultra-DMA (UDMA) transfer modes up to Mode 4, which is 66MBps (called UDMA/66 or Ultra-ATA/66).

• 80-conductor cable now mandatory for UDMA/66 operation.

• Added automatic detection of 40- or 80-conductor cables.

• UDMA modes faster than UDMA/33 are enabled only if an 80-conductor cable is detected.

ATA-5 includes Ultra-ATA/66 (also called Ultra-DMA or UDMA/66), which doubles the Ultra-ATA burst transfer rate by reducing setup times and increasing the clock rate. The faster clock rate increases interference, which causes problems with the standard 40-pin cable used by ATA and Ultra-ATA.

To eliminate noise and interference, the new 40-pin, 80-conductor cable has now been made mandatory for drives running in UDMA/66 or faster modes. This cable was first announced in ATA-4 but is now mandatory in ATA-5 to support the Ultra-ATA/66 mode.

This cable adds 40 additional ground lines between each of the original 40 ground and signal lines, which help shield the signals from interference. Note that this cable works with older non–Ultra-ATA devices as well because it still has the same 40-pin connectors.

The 40-pin, 80-conductor cables will support the cable select feature and have color-coded connectors. The blue (end) connector should be connected to the ATA host interface (usually the motherboard). The black (opposite end) connector is known as the master position, which is where the primary drive plugs in.

The gray (middle) connector is for slave devices. To use either the UDMA/33 or UDMA/66 mode, your ATA interface, drive, BIOS, and cable must be capable of supporting the mode you want to use. The operating system also must be capable of handling Direct Memory Access.

Windows 95 OSR2 or later, Windows 98/Me, and Windows 2000/XP are ready out of the box, but older versions of Windows 95 and NT (prior to Service Pack 3) require additional or updated drivers to fully exploit these faster modes. Contact the motherboard or system vendor for the latest drivers.

For reliability, Ultra-DMA modes incorporate an error-detection mechanism known as cyclical redundancy checking (CRC). CRC is an algorithm that calculates a checksum used to detect errors in a stream of data. Both the host (controller) and the drive calculate a CRC value for each Ultra-DMA transfer.

After the data is sent, the drive calculates a CRC value, and this is compared to the original host CRC value. If a difference is reported, the host might be required to select a slower transfer mode and retry the original request for data.