12" Floppy Disks

Paul Koning paulkoning at comcast.net
Tue Sep 15 12:03:34 CDT 2015

> On Sep 15, 2015, at 12:28 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:
> ...
> AFAIK the RK04 never existed. The RK02 and RK03 were re-badged Diablo Model 30
> drives, the 02 being low density and the 03 high density. The RK05, very well known
> was a DEC drive of the same capacity, physical track format, etc as the RK03 (that is
> 'high density, about 2.5 MBytes on a disk). 

There was also an RK08, as I recall -- same platter as the RK11/RK05 but 16 sectors per track instead of 12.

If I remember correctly, that same 16-sector platter was used in the IBM 360 model 44 which had an RK05 lookalike built into the CPU cabinet (on the side).  I never used it; not sure if OS/360 supported it, that might have been PS/44 only.  If yes, one wonders if it was fixed size sectors, a rather un-OS-like thing to do...


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