Filename: UDMACABL.TXT
WWW URL: http://www.firmware.com/support/bios/udmacabl.htm
FTP URL: ftp://ftp.firmware.com/text/udmacabl.txt
Revision: 02/02/99 TLS Micro Firmware Technical Support
Summary: General information on 80-conductor ATA cables developed
for use with UDMA-33 and UDMA-66 hard drives.
The ATA-4 specification defines an 80-conductor cable that can be used with UDMA drives. This cable is further defined in SFF-8049, a document published by the Small Form Factor Committee.
The purpose of this new cable is to improve the signal quality for high-speed transfers over the ATA (IDE) interface. This is accomplished by adding 40 ground wires to the existing 40 wires to provide a ground between each signal wire and provide the effect of a common ground plane. The connectors also contain a ground bus which ties together the ground wires.
The connectors on the cable are color-coded - the host interface connector is blue, the device 0 connector (at the other end of the cable) is black, the device 1 connector (in the middle) is gray. The retainers on all of these connectors are black. These cables are color-coded to prevent them from being installed backwards. In some configurations, hard drives may be damaged if the cable is installed backwards.
These cables can be used with master/slave drive jumpering or with cable select drive jumpering. See our document, CABLESEL.TXT for more information on cable-select.
http://www.firmware.com/support/bios/cablesel.htm
These cables can be used instead of regular IDE cables with any IDE drives. It is recommended to use the 80-conductor cables with UDMA drives when used on high-speed UDMA-33 controllers. A new specification for faster transfer rates, UDMA-66, may require the use of these cables.
More information is available on a website set up just for these cables by Circuit Assembly, who makes these cables under the brand name ATAS. The URL for that website is:
We sell these cables in two sizes, 18" and 24". Here are the measurements from connector to connector for all sizes, followed by our part numbers:
18" cable: Blue 12" Gray 6" Black UCAB1824" cable: Blue 12" Gray 12" Black UCAB24
24" cable: Blue 18" Gray 6" Black UCAB18/6
For a while we also sold a 24" cable with 12" between each connector. This was discontinued by the manufacturer, who cited technical reasons for not continuing to make this cable. (As of 02/02/99, we still have some of these in stock).