While looking for something completely unrelated (namely the Rock Ridge extensions to ISO 9660), I came across a cache of old X3T9 committee documents from 1990. In retrospect I’m a little surprised that I hadn’t found these earlier, since the archive appears to have been published on one of Walnut Creek CD-ROMs circa 1994, but I’m not sure how long it’s been online.
What’s interesting is that the Walnut Creek archive appears to overlap with the X3T9.2 archive that has available for a long time, but contains numerous documents that the X3T9.2 archive does not. Notably there’s a directory with CAM Committee documents. While the CAM Committee’s primary objective was to define a Common Access Method (CAM) for software accessing SCSI devices, an effort that ultimately went nowhere, the CAM Committee also started a rather more successful side project, the AT Attachment (ATA) standard.
The archive is far from complete, but it does include one complete ATA draft, revision 2.1 from June 11, 1990. That’s one revision older than the oldest ATA draft I was aware of until now, which is revision 2.2 from August 1990. The rev 2.1 draft is provided as a ZIP archive containing WordStar files, which is excellent for seeing exactly how the draft was edited (and the WordStar files include a couple of editorial comments that do not show up in the printed version), but the downside is that getting from WordStar to PDF was not entirely trivial. In the end I was able to produce a PDF of ATA Rev 2.1 in 2-up format that’s quite similar to the scanned documents in the X3T9.2 archive.
Even better, the Walnut Creek archive includes what appears to be the very first and quite incomplete ATA standard draft from March 30, 1989. Said draft also provides a hint why a SCSI oriented committee started ATA in the first place: The early ATA drafts also included a specification of EATA (Extended AT Attachment), a SCSI pass through mode of ATA devices (completely separate from and much older than ATAPI).
Sadly the initial draft—which is so old that it’s called DAD, for Disk ATBus Definition, rather than ATA—does not include the EATA sections. In the next oldest currently available draft (revision 2.1), EATA had been already removed again. ATA revisions 1.x appear to have included the SCSI pass through functionality defined by EATA.
EATA was the brainchild of DPT (Distributed Processing Technology), one of the larger SCSI HBA vendors. An overview of EATA can be found here. I don’t believe anyone besides DPT implemented EATA, but the idea behind it was quite interesting.
CHM’s oral history of Dal Allan describes how EATA was created by DPT and desired by Quantum, but WD successfully fought to remove it from the standard for cost reasons, only to implement the same idea (SCSI pass through over ATA) as ATAPI a couple of years later.
The first ATA draft from March 1989 notably already defines the IDENTIFY DRIVE command as well as READ/WRITE MULTIPLE, but there is no sign of DMA support yet. The DASP signal for letting drive 0 detect drive 1 was also already defined, although the details were refined many times since then.
Finding the very first ATA draft is something I doubted would ever happen. Now I wonder if the revision 1.x ATA drafts might eventually turn up, too.
The list of early ATA drafts on this site has now been appropriately updated.