Anybody has Control Data (CDC) disk packs for 841 and 844 disk drives to spare with?

P Gebhardt p.gebhardt at
Mon Jun 5 10:01:32 CDT 2017

Hi Jim,

>I moved a system with 4 300mb memorex 10 (or so) platter drives eons 
>ago, which had been running for a year or more.  After setup and service 
>it ran 2 hours before eating one of the drives.  That was and is the 
>last time I'll ever run drives w/o sealed HDAs.


I heard from a former field engineer in the past that after service or parts replacement, they let the drive in stand-by with the ventilation turned on run for a whole day just to make sure that there are as little as possible remaining particles within the disk pack compartment that could lead to a head crash...

>I'll take emulated drives or whatever attached to the artifact systems >any time, vs. running original disks subsystems.  It's good that the 
>work to get the replacements going is being done now while the people 
>still familiar with the OSs are still around or people who can do that, 
>as of course doing it later if one wants to restore and run systems like 
>that further down the road will make it much harder to do.

True that it is nowadays more than ever important to have drive emulation for the vintage computer systems. And even more that there are people in our community working on this while knowing the operating systems, as you state. 
There are less and less spare parts (particularly drive heads and disk packs) out in the wild and I guess even less people who know how to service these beasts, provided they have all alignment and service tools at hand. 

At some point in the future, even doing a demonstration of such drives while working will become more and more critical. 

However, there are still disk packs out there with software being very valuable to be transfered for historical or other reasons. For that sake, it would be good to have working drives somewhere on this planet. 

Admittedly, I don't even know, who has as of now working drives with non-sealed HDA from the 1960s/70s era. I guess that working CDC SMD drives (9760/9762/9764/9766) and OEM'ed versions of them might still be around, as they were quite spread in the 1980's.
Maybe some day, we will be able to reproduce or get reproduced some of the disk heads for disk drives with non-sealed as well as sealed HDAs or even reproduce new platters that do not require a high density. Let's see.

Personally, I find these drives super interesting and challenging due to the combination of electronics and mechanics and I would like to try reviving a few of my CDC drives, as I was able to obtain quite some service tools and field testers for them. But I haven't found the time, yet.

Best regards,

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