Thanks Bruce. Data General actually went into the 14" drive manufacturing business, platters, heads, positioner, spindle, and all? I've been assuming that they sourced the drive assembly OEM and then built their finished product around that.
Yes, the associated 8" FDD is DSDD so "quad"; manufacturer is Qume (842?) in that particular system. I imagine that DG might have used others. Christian Kennedy mentioned MPI as the FDD manufacturer (9404B?), and possibly for the HDD, so I rooted around in the CDC documentation on Bitsavers (thanks Al!) and I see that the 9730 MMD used a dual head per surface configuration and from https://bitsavers.org/pdf/cdc/discs/CDC_Drive_Models.txt this: Model Media 1st Ship Unformatted Size Name 9730-12 14" 5/77 12.9 Fixed 9730-24 14" 5/77 25.8 Fixed That all looks promising, however the technical details don't match very well unless the unit in the photo is actually 12.5MB capacity [Model 6099] in which case the 9730-12 matches well with one platter, one servo head (lower surface), and two recording heads (upper surface). The 9730-24 stacks two platters and doubles the number of recording heads (the upper platter has the pair of heads on the underside). See: https://bitsavers.org/pdf/cdc/discs/brochures/CDC_9730_MMD_Brochure_Oct76.pdf https://bitsavers.org/pdf/cdc/discs/mmd/64709700r8_MMD_9730-xx_ProdSpec_Mar78.pdf https://bitsavers.org/pdf/cdc/discs/brochures/CDC_9730_MMD_Brochure_May79.pdf The CDC / MPI finished product uses a SMD interface and stacks the drive electronics over the drive assembly. It seems reasonable to conclude that DG acquired the drive assembly from MPI and then did their own electronics to a proprietary non-SMD interface, which would explain the cabling visible in the photo. The earlier product brochure is October 1976 (and is light on details), MPI ships the 9730-12 (finished product) in May 1977, the family engineering spec (rev 8) is March 1978, the second product brochure is May 1979, and the DG drive assembly in the photo seems to be mid-1981 based on the bad block sticker. Not sure how much earlier DG introduced the Model 6099 but this seems like a reasonably consistent timeline. The clear head photos in the second product brochure aren't an exact match, but they are close. Perhaps MPI made some engineering tweaks over the lifespan in the drive assembly? Bruce, are you sure that DG didn't OEM the drive assembly from elsewhere, and in particular MPI? -----Original Message----- From: Bruce Ray via cctalk <[email protected]> Sent: Sunday, October 27, 2024 7:02 PM To: Paul Birkel via cctalk <[email protected]> Cc: Bruce Ray <[email protected]> Subject: [cctalk] Re: Identify 14" HDD with two heads on single arm In 1979 Data General started manufacturing its own two line of 14" Winchester disk drives - a 12.5 MB [Model 6099] and a 25.5 MB [Model 6103] version. A "quad-density" 1.2 MB 8" floppy diskette drive or two were often part of the system for installation and backup purposes. There is usually an ID plate on the back of the disk drive that contains the model number and DG Product number (i.e. 005-xxxxx-yy) of that specific unit. Bruce Ray Wild Hare Computer Systems, Inc. Denver, Colorado USA [email protected] ...preserving the Data General legacy: www.NovasAreForever.org
