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What is ATA/66?

R. Kayne
R. Kayne

Advanced Technology Attachment (ATA) is an interface standard for connecting storage components to an IBM-type personal computer. ATA/66, standardized in 1999, is one variety.

The original ATA interface used parallel 40-wire cables and had the ability to host two drives on a single cable. This was accomplished using a master/slave configuration. This basic model endured through the ATA/33 specification. With the introduction of ATA/66, the 40-wire cables were replaced by 80-wire cables for even-faster data transfer speeds, theoretically reaching up to 66.6 megabytes per second (MBps). Both types of cables continued to use 40-pin connectors.

Woman holding a disc
Woman holding a disc

The many designations for the various flavors of ATA that developed over the years can be difficult to keep straight. Other designations for ATA/66 are ATA-5, the standard under which it falls, and Ultra ATA/66. The specification also corresponds with the Ultra Direct Memory Access (UDMA) 3-4 transfer modes. If this isn’t enough to confuse even a dedicated computer enthusiast, the name is sometimes used interchangeably with Enhanced Integrated Drive Electronics (EIDE) and ATA Packet Interface (ATAPI-5). The ATAPI-5 standard incorporates additional commands to control CD-ROMS and tape storage units that use the specification.

All parallel ATA cables are limited to 18-inches (45.7 centimeters) in length. This makes them bad candidates for external devices, and can also create difficulties inside the computer. The ultra-wide cables block airflow and are difficult to route.

This problem was eventually addressed by later-generation serial ATA (SATA). Four-wire SATA cables are thinner, with a smaller interface and greater data transfer speeds than original ATA. Original ATA is now referred to as parallel ATA (PATA) to differentiate it from SATA.

Older hard drives made to the ATA/66 specification still require legacy PATA cables. If upgrading to a SATA drive, computer users should be sure their motherboard supports SATA. Motherboards manufactured prior to 2004 might not include this support. Unlike ATA, SATA uses point-to-point control, meaning that each drive has its own cable. For this reason, SATA-enabled motherboards typically have several SATA interfaces, or the ability to run a redundant array of independent disks (RAID).

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Discussion Comments


@umbra21 - Yeah, when you've got all the parts in front of you, a desktop computer isn't that difficult to put together. All the different bits only slot into one place and all the plugs are different sizes. As you say, the ATA was quite large, but the SATA is much smaller and more efficient, like a lot of things in computers these days!

I actually think it's a shame more people don't get to know the insides of their computer, if only because it helps to give it a dust every now and then.


My father taught computer technology in a high school a decade ago and I remember having to help him put together a bunch of computers he had managed to get. It was before computer technology was so widely promoted (I was still in a typing class in my own school!) and I thought it would be really difficult to put together a computer.

Turns out it wasn't that difficult. Dad managed to get deals on several parts with different companies and he had some kind of method to wipe the hard drives and install his own standard set up, so we had to do a lot of connecting. I actually didn't know that this particular plug was called an ATA66 (or possibly a different ATA connection). I do remember that it was my least favorite part, because it was tough to line up such a long plug.


no, pata is pata

the only thing to note w/ PATA is:

1) putting two drive, on one cable they will both run at the speed of the slower drive

2)make sure if you use cable select on the pins your also use a cable select cable


Hi wiseGEEK!

WARNING: Novice getting hands dirty!

I have a Maxtor 80G PATA 133 drive bought last week which will [i]not[/i] work in a brand new caddy that I have. I have a 30G Maxtor ATA 133 drive bought more than 3 years ago that works in the caddy (both the drives work when connected direct to the IDE cable).

I have a Seagate Barracuda Ultra IDE that also works fine in the caddy. Could the specification "P"ATA be somehow making a difference? Is it possible to buy a PATA caddy? If this is the case, would it work with all my older drives?

Any replies would be most welcome.

This is a ***t-hot site! Could I put a link to here in my "home" forum ( )? Please let me know.

Many thanks! :-)

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