Slim pickings on CMI drive, but here's some:

IBM\ufffds original hard drive for the AT had a 40-millisecond average seek time and held 20 megabytes. That drive, built for IBM by a company called CMI, was unreliable. IBM eventually switched to a different supplier, and CMI went bankrupt.

Most clones contain reliable drives that go faster (28 milliseconds) and hold more (40 megabytes and beyond).

[link|http://www.gis.net/~poo/27ibm.html|Link] for the above.

Also, [link|http://www.rdrop.com/~jimw/j-hist.shtml|CMI Model 6426-S Hard Disk Drive].

This is the item that almost single-handedly ruined IBM early in the Personal Computer age.

CMI was the only company at the time that could produce a drive that would meet the then almost unimaginable specifications for seek time that IBM had required for a hard drive for their new (at the time) IBM 'AT' computer.

The drive was fast alright, but had a hidden flaw... The drive gained its speed by using a rotary actuator to move the heads rather than the more traditional stepper motor. This required that a 'servo' track be written on one of the disk platters to provide the information that the drive logic used to center the heads on the selected track.

What quickly became apparent soon after the computer went in to production, was that the drives had a operational life of about three months! A flaw in the drive circuitry gradually erased the servo track, causing the drive to be unable to position the heads accurately which either began to corrupt data, or one day the drive would just refuse to function.

Frantic (and very expensive) efforts were made to do 'damage control' on the situation, and IBM replaced thousands of these drives only to see the replacements start to fail as well. This whole fiasco severly damaged the reputation of both IBM and the 'AT' computer, and it was some time before either fully recovered.

Nearly all of the CMI drives were eventually recalled and replaced, (with drives from a different manufacturer and somewhat relaxed specifications) and the entire lot of drives were eventually thrown on a barge and dumped in the ocean off of the Florida coast in order to create a foundation for a new submerged reef.

To their credit, IBM did try to fix the problem.

Post #74,889 by a6l6e6x 1/16/03 11:18:45 AM Reply	Slim pickings on CMI drive, but here's some: IBM\ufffds original hard drive for the AT had a 40-millisecond average seek time and held 20 megabytes. That drive, built for IBM by a company called CMI, was unreliable. IBM eventually switched to a different supplier, and CMI went bankrupt. Most clones contain reliable drives that go faster (28 milliseconds) and hold more (40 megabytes and beyond). [link\|http://www.gis.net/~poo/27ibm.html\|Link] for the above. Also, [link\|http://www.rdrop.com/~jimw/j-hist.shtml\|CMI Model 6426-S Hard Disk Drive]. This is the item that almost single-handedly ruined IBM early in the Personal Computer age. CMI was the only company at the time that could produce a drive that would meet the then almost unimaginable specifications for seek time that IBM had required for a hard drive for their new (at the time) IBM 'AT' computer. The drive was fast alright, but had a hidden flaw... The drive gained its speed by using a rotary actuator to move the heads rather than the more traditional stepper motor. This required that a 'servo' track be written on one of the disk platters to provide the information that the drive logic used to center the heads on the selected track. What quickly became apparent soon after the computer went in to production, was that the drives had a operational life of about three months! A flaw in the drive circuitry gradually erased the servo track, causing the drive to be unable to position the heads accurately which either began to corrupt data, or one day the drive would just refuse to function. Frantic (and very expensive) efforts were made to do 'damage control' on the situation, and IBM replaced thousands of these drives only to see the replacements start to fail as well. This whole fiasco severly damaged the reputation of both IBM and the 'AT' computer, and it was some time before either fully recovered. Nearly all of the CMI drives were eventually recalled and replaced, (with drives from a different manufacturer and somewhat relaxed specifications) and the entire lot of drives were eventually thrown on a barge and dumped in the ocean off of the Florida coast in order to create a foundation for a new submerged reef. To their credit, IBM did try to fix the problem. Alex "No man's life, liberty, or property are safe while the legislature is in session."\t-- Mark Twain
Post #74,945 by deSitter 1/16/03 5:17:33 PM Reply	Re: Slim pickings on CMI drive, but here's some: Wow, that's new to me. This is a completely different issue than the one with the Seagate drives. In fact I'm sure I've never heard of CMI (not the same as CMS, a third party supplier of PS/2 SCSI hardware). Our ATs were delivered in early 1985 - when did the very first IBM AT ship? We used our AT as a network server way back then - a real, original IBM NETBIOS network. -drl
Post #75,004 by a6l6e6x 1/16/03 9:52:06 PM Reply	First ATs were shipped in 1984. So you may... have been lucky. Working for IBM, I had a pre-release version w/CMI drive. Alex "No man's life, liberty, or property are safe while the legislature is in session."\t-- Mark Twain
Post #75,017 by deSitter 1/16/03 11:08:45 PM Reply	You could hear.. ..the gentle whirring of the stepper motor as it moved the head around. It was certainly a Seagate drive. Funny, I can almost imagine the layout of the AT mobo, not having seen it in 17 years. -drl

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