Early 3.5" Floppy Drives

Allison ajp166 at bellatlantic.net
Thu Dec 15 12:52:57 CST 2005

>Subject: RE: Early 3.5" Floppy Drives
>   From: Roger Merchberger <zmerch at 30below.com>
>   Date: Thu, 15 Dec 2005 13:40:44 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>Rumor has it that Allison may have mentioned these words:
>>Size   density  format   writeclock
>>8"       DD      MFM     1000khz
>>8"       SD       FM      500khz  (8"SSSD 241k CP/M standard)
>>5.25     DD      MFM     500khz (40track is 360k, 80track 720k)
>>5.25     SD       FM     250khz
>>3.5"     HD      MFM    1000khz (1.44mb) (looks like 8" different CHS)
>>3.5"     DD      MFM     500khz (720k)   (same rate as 5.25 DD and 8" SD)
>>3.5"     ??       FM     250khz (not used obsolete)
>3.5" FM was used for microcomputers - the Tandy Portable Disk Drive (OEMmed 
>by Brother, IIRC) was 40 tracks, 2SPT FM w/100K storage. Serial port 
>driven, and worked with the Tandy Model 100/102/200 laptops. In my Service 
>manual for the critter, it did mention the density, but I don't have that 
>handy. DD disks worked just fine on it (read: data life at least into the 
>10 year range), but HD didn't work so well, IIRC.
>The TPDD2 was also FM, but used an 80 track drive (set into 2 banks for 
>compatibility with the TPDD1) for 200K storage.
>Roger "Merch" Merchberger

;) it's obsolete.  I know there were at least 20 formats not mentioned
that were "out of the mainstream" so more exceptions are known.
However looking at the clock rates mentioned I'd guess it can be done. ;)


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