History (1987): Conner CP341 HDD

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1987: Conner CP341 Drive
Emergence of ATA as widely used interface

Why it’s important
In the early days of computing it would take a specialist hours to connect a disk drive to its computer. Now because the connection has become an industry standard, a consumer can buy a drive at a local store, plug it into their computer and be operational in minutes. The most common standard drive interface is SATA, SATA, the latest invocation of ATA (IDE) first conceived by Bill Frank at Western Digital in 1984 and which then broke through to commercial success beginning with the Conner CP341 in 1987.

As an intelligent drive interface universally adopted for most computers, ATA (IDE) was an enabler of the acceleration of disk drive capacity that began in the early 1990s.

Discussion:
This interface development was initially conceived by Bill Frank of Western Digital in the fall of 1984 as a means of combining the disk controller and disk drive electronics, while maintaining compatibility with the AT and XT controller attachments to a PC without changes to the BIOS or drivers. WD floated that idea by its largest customers, IBM, DEC, and Compaq in the winter and spring of 1985. Compaq showed interest, so Bill Frank collaborated with Ralph Perry and Ken Bush of Compaq to develop the initial specification.

WD formed a Tiger team in the spring of 1985 to build such a drive, using externally purchased 3.5″ HDAs (Head Disk Assemblies), but initially just provided ATA to ST506 controller boards that Compaq hard-mounted to 10MB and 20MB 3.5″ Miniscribe ST506 drives for their Portable II computer line, announced in February 1986 [3, 15, 20]. Compaq also worked with Control Data (CDC) to put the IDE interface into a 5-1/4″ half-height 40MB Wren drive for the Compaq DeskPro 286 computers but it isn’t clear how many actually shipped.

The ATA interface didn’t really take off, however, until it was fully integrated into Conner Peripheral’s CP34x line of 3.5″ drives, with the CP341 announced in Compaq’s Portable III computers in February 1987 and the Conner CP342 announced in June 1987 for other OEMs. The CP342 was apparently then replaced by the CP344, which had the same specs and was the first ATA drive tracked by Jim Porter in Disk/Trend reports. Compaq had invested heavily in Conner, in order to do a joint ASIC development for this integration and assure supply, resulting in Conner becoming the fastest growing start-up in history, by exceeding $1 billion in revenue in just 3 years.

CDC was not interested in 3.5″ drives at that time, since they were focused on the 5.25″ SCSI high-performance market.

WD bought Tandon in 1988 and became one of the largest drive suppliers in the world, while shipping almost exclusively (P)ATA/SATA drives. Seagate acquired CDC’s disk drive operations (Imprimis) in 1989, Conner in 1996, and Maxtor in 2006, and also became one of the largest suppliers in the world, with the bulk of the drives having the (P)ATA/SATA interface.

ATA was specified by the Common Access Method (CAM) committee, an ad hoc industry group, as ATA in April 1989 and adopted by the American National Standards Institute in January 1993. It is currently supported by T13, a Technical Committee for the International Committee on Information Technology Standards and is in its eighth major version. Throughout its evolution, the ATA standard has maintained a high degree of compatibility with earlier versions, while providing higher performance, additional functions and/or additional device support.

Most early products did not describe the interface as either ATA or IDE but instead used descriptive phrases such as ’embedded AT controller.’ IDE was a popular name for the interface in the early 1990s but ATA became the dominant name thereafter. With the introduction of SATA in 2000 ATA became Parallel ATA or PATA.

The market demand for ‘enterprise-like’ reliability in PC drives led to the development of Self-Monitoring. Analysis and Reporting Technology, a specification written by Fujitsu, Hewlett Packard, IBM, Maxtor, Quantum, Seagate, and Western Digital, with active participation of other companies. This was distributed as SFF-8055i and incorporated into ATA-3.

A significant enhancement made in ATA-4 was the incorporation of a SCSI-like packet interface know as ATAPI (ATA Packet Interface). ATAPI has been specified by the Small Form Factor (SFF) Committee to support devices other than HDDs, including CD and DVD devices.

Over the past 20 years, well over 80% of all HDDs shipped have used a version of the ATA interface. The level of intelligence in the HDDs has been increased every year, with the addition of more sophisticated data encoding, ECC, defect management, zoned recording, serial interfaces, etc, yet all ATA drives still support the original ATA command set, assuring compatibility across generations.

All of the 3.5″ PATA drives used the 40-pin connector that was originally conceived by Ralph Perry but a 44-pin variant, incorporating the power pins, was introduced by Conner that became the forerunner of the 50-pin SFF-8212 connector specified by the SFF Committee for 2.5″ ATA drives in 1995. The latest version of ATA is SATA 3.0, which is currently shipping in 2TB 3.5″ drives and 1TB 2.5″ drives, while transferring data at 6Gb/s over a common 7-pin serial interface with SAS (Serial SCSI).

The major reasons that ATA has become
the most successful disk drive interface are:
1 Ease of integration: the emulation of the WD1003 controller implementation in the PC/AT allowed booting without BIOS modifications, initially up to 528MB and subsequently to 137GB, although there were a number of other barriers to increased capacity that also had to be overcome along the way
2 Low host cost and complexity: by separating the WD1003 functions from the host functions, the cost of the host adapter was reduced to the point where it could be integrated first on to the motherboard and then into the ‘Southbridge.’
3 Acceleration of technology advancement: Like SCSI and the other ‘intelligent’ interfaces, this broke the ‘controller barrier’ but IDE/ATA was the only one that also had the above two advantages, providing a significant reduction in time-to-market and enabling ATA to rapidly catch up to the high end areal density growth curve, where it became the disk capacity leader, with the lowest cost per gigabyte.

Provenance note: This article was written by Tom Burniece with contributions from Tom Gardner and I. Dal Allan. Version 27 was reviewed and approved by the Computer History Museum’s Storage SIG on July 21. 2011 and posted as Compaq/Conner CP341 IDE/ATA Drive at the CHM web site.