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The Secret History of ATAPI (os2museum.com)
100 points by finite_jest 12 days ago | hide | past | favorite | 38 comments

An interesting point that isn't made super clear in the article: ATAPI basically _is_ SCSI, just encapsulated in ATA commands over an ATA bus. This is possible because SCSI is more a network protocol with a lot underlying physical encapsulations. The PI in ATAPI stands for [SCSI] Packet Interface.

So it's no wonder that ATAPI killed off SCSI CD drives in PCs. Since it _was_ SCSI, it really just killed off having to buy an extra host bus adapter card to send the same command set.

> it really just killed off having to buy an extra host bus adapter card to send the same command set.

Sometimes that stuff could get pretty baroque. Back in the day I had a 20 MB HD for my Atari 8 bit computer, which involved an adapter from the Atari proprietary bus to SCSI/SASI, then a second adapter from SCSI to the MFM HD interface. You needed one of the custom DOSes to make use of it, as the standard Atari DOS had never envisioned things like hard drives.

We had a lot of SCSI devices in my house, and I think maybe like, 2 devices had the same connector. Even ZIP and JAZ, both by iomega, couldn't agree. The Atari ST in my place also has an ACSI connector, which is my guess, SCSI but yet more different somehow.

At that point I didn't even want plug'n'play or hotplug because getting something set up once was enough for you to never desire to change it.

I still have a huge crate of SCSI cables for my obsolete gear. Stuff like 25 pins to 50, 50 to 68, 68 to 80 pins, HVD and LVD cables with a bunch of various connectors, cables with integrated passive or active terminators, terminators that only terminate the high bits, cables with 3 connectors (yes, really) for devices with only one SCSI port, etc.

Like the old saying goes, "there are valid technical reasons that demand that you sacrifice a black goat here and there to your SCSI chain".

SCSI was the unobtainium of my childhood. There was one day where we had a borrowed SCSI card in the family computer for a Zip drive and a scanner and I felt like I lived in the future for a brief moment.

SCSI was definitely whizzy for its day, but man, was it ever finicky to get working and keep working. As a previous commenter noted, if you got a setup that worked you were reluctant to change anything.

USB Mass Storage (bulk only, at least) is also SCSI-based.

The old USB mass storage class was custom, but USB 3.0 and up enclosures should do UASP (USB Ander SCSI Protocol).

No, it's always been SCSI:


UAS is yet another variant of passing SCSI commands through USB.

Thanks, TIL. Always thought the new thing about UASP was direct SCSI support, but it actually seems like the main problem with BOT was it being fully synchronous, so only one request in flight at any given time.

I assume you mean "USB Attached SCSI Protocol" :)

To continue the circle of life there is SCSI/ATA translation for tunneling ATA in SCSI.


Hard disks attached to the system as an ordinary mass storage device tend to disappear completely from the bus in case a bad sector has been hit. Learned about this while building RAID over USB at one of my former employers (don't ask). While SAT is virtually a passthrough over USB avoiding such disappearances and its presence is mandatory in, for example, data recovery scenarios.

Before(?) SAT, there was Cypress' ATACB for the same purpose: https://www.cypress.com/documentation/datasheets/cy7c68300c-...

it woulg be wonders if you could give a history of the JAZZ drive and the other iomega things


Ah, Jaz. My college buddy had one and we christened it the WORN Drive: Write Once, Read Never.

I had one and it was horrible. It was a fancier version of /dev/null.

I had a bad disk once and whatever happened affected the drive head. This of course meant that every other disk I had was then similarly corrupted. I know people that used many Zip drives and were quite happy with them, but I never trusted Iomega again after that.

Love it...

We can say same of DATA

"Dicussed, Archived, Translated, Attributed (Falsely)"

The weirdest thing was the sound cards were basically "everything you need for multimedia" at the time. eg. Joystick, Midi and CD-ROM connectivity, etc were all on the sound card.

So before ATAPI we still didn't buy a specific CD-ROM interface card to connect CD-ROM drives. We just bought a sound card that had the CD-ROM interface we needed. You just had to make sure you bought the right CD-ROM connectivity for your sound card.

In the early days there were a lot of bundles you could buy that were a sound card + CD-ROM drive, and sometimes even speakers and software, eg:


My first PC was a used 486DX in the mid-90s, and it had a Sound Blaster 16 (ISA) with the IDE connection on it for a CD-ROM drive. However, the motherboard also had its own dedicated primary and secondary IDE channels already, so it seemed simpler to just use those when I bought myself a CD-ROM drive, and avoid whatever hoops would have to be jumped through to make the sound-card-connected one work.

There were plenty of cool oddities back then. I had a CD-ROM drive which had a full set of playback and volume controls, a headphone jack, and an IR receiver for the associated remote control. Since back then most CD-ROM drives also had an analog audio path directly to the sound card (through a separate thin cable), you could play a music CD without involving the operating system other than to adjust the master volume (though the operating system could also control the playback if it desired).

Nowadays it's all gotten boring, all we can do is rip the digital audio data through the operating system and write it to the sound card.

On the early DVD times also. Or you can play cds just from drive wihout system. Funny times.

Those DVD sound card+drive bundles weren't for connectivity to the drive in that era however (ATAPI and SCSI were the only standards for DVD-ROM drives). The bundle was to get a card with a hardware MPEG2 decoder since MPEG2 was taxing on the systems of the era.

With the exception of the TV out those cards were a terrible investment though. CPUs went from Pentium 120Mhz to Athlon 1000Mhz within 5 years and the playback software got optimized massively as well (CyberLink PowerDVD was a big success since it could enable MPEG2 playback on even a lowly Pentium MMX).

In fact i remember being given a couple of those cards in that era since pretty much everyone could play DVDs without the dedicated hardware and no one could be bothered setting up the drivers for it.

I had a P4 (~1.6GHz) at one point and I remember DVD playback even on that system was a bit flaky. Like it was mostly good but would hitch for a second or two every fifteen minutes. Just often enough to make it pretty annoying for trying to actually watch a full movie.

If you were still in that era i'd say make sure the drive is in DMA and not PIO mode!

The drives would operate in a fallback mode called PIO unless you installed specific drivers for the DVD drive. The symptoms you describe sound like this. 1.6Ghz was definitely enough for MPEG2 decoding.

Apple started using software DVD decoding once the G3 hit 500 MHz (with the dual USB white iBook)

There was definitely a period in the early 2000s where having CD-RW plus separate DVD-ROM drive was a somewhat standard "premium" configuration— it obviously was great for duplication, or you could do stuff like load up multiple Encarta discs at once, or have both Diablo II discs in at the same time, whatever.

Back ages ago, I had one of the CD-ROMs with full audio controls and analog out, and used it along with a bare AT PSU and one of those drive-bay equalizers as a desktop CD player, no proper computer involved anywhere.

In the same vain, as a child of about 10 I used to use a CD-ROM drive hooked up to a PSU and headphones to listen to music in bed. It was lovely as a portable CD player would have been totally unaffordable to my family at the time.

It's not weird at all! There was a brief window of time between CD-ROMs and multimedia capability becoming affordable and them becoming ubiquitous in the PC market. During this time the "Multimedia PC" [1] standard / branding was introduced to differentiate PCs that had that capability.

If you were an OEM PC builder back in the 90s on margins so thin they could only be detected using an electron microscope, you'd be looking for the cheapest way to qualify for yet another sticker on your beige box. Naturally you'd gravitate towards solutions that minimised your part count. So we got sound cards with CD-ROM interfaces.

[1] https://en.wikipedia.org/wiki/Multimedia_PC

Interesting that throughout the entire long article, the acronym for ATAPI was used without ever being described. It's quite the rabbit hole.

ATAPI = "ATA Packet Interface" https://en.wikipedia.org/wiki/ATA_Packet_Interface

ATA = "AT Attachment" https://en.wikipedia.org/wiki/Parallel_ATA

AT = "Advanced Technology" (possibly apocryphal or a retronym) https://en.wikipedia.org/wiki/IBM_Personal_Computer/AT

Ah, those early days of CD-ROMs… I remember when they first came out, a blank CD-R disc was around $100. I remember trying to think of a use case for what could merit that level of expense. A couple months ago, while cleaning up around my desk, I ended up listing a spindle of about 500 blank CD-Rs on the free to a good home category on craigslist. It took a couple tries to get someone who actually came to pick it up. If only I had a time machine, I could have sent it to my 20-something self in the early 90s and sold them for $50,000 and then put that money into Apple stock.

Where's my damn time machine?

Someone reads out atip, discovers disks manufactured by a company that doesnt exist yet and Xfiles raids your house.

There are so many ways to mess up. If we got time travel in the next ~40 years Google could probably catch casual time bandits by tracking early meme and emoticon usage.

I got my first PC in August 1994 and it had a Mitsumi 2X ATAPI CD-ROM. Everything I read said that Linux didn't support them yet. The drive worked fine in DOS/Win 3.1 which is what the computer shipped with.

I downloaded Slackware 2.1 on floppy disks and installed from that. By the next Slackware release my ATAPI CD-ROM was supported and I mail ordered a CD and everything worked fine.

Ah, memories. :-) I used to work on the ATAPI CD-ROM drives produced by Singapore's Creative Technologies.

I wonder how creative stays in business. I see they still make sound cards, and they sell speakers/headsets. But they’re not exactly ubiquitous like they were back in the day.

the varying SCSI plugging over its life is the bane of any modern day "can I read that tape" because you need the tape mechanicals to line up, but then you need the cable to be the right kind of left handed, reverse-frob, biwhiskit with bivalve mounted cliperators.

ATAPI never had this problem as I understand it.

Great that os2museum.com is hosting articles. It reminds me of the Internet of the past I loved. Decentralised and fine, like an unexplored forest.

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