Subject: Floppy Disk Speeds

From: [email-masked] (Charles K. Neuberg)
Date: Tue, 20 Apr 1993 20:54:54 GMT

Hi, and forgive the intrusion but you folks seem like real hackers and
should know this one off the top of your heads.

How fast does a floppy spin?  Typical speeds for 8", 5.25", 3.5".
Don't need any specific brand names...somebody asked me and I just
don't know.

email is great unless you think everyone should know.

Thanks.

Chuck
[email-masked]

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From: [email-masked] (Charles Lasner)
Date: Wed, 21 Apr 1993 04:17:13 GMT

>Don't need any specific brand names...somebody asked me and I just

8" floppies are typically 360 RPM and 500 KHz recording regardless of format.
Either FM or later MFM is used.

5.25" early floppies are 250 KHz 300 RPM.  Later ones are the same as the 8"
drives.  Very early drives were usually FM.  Most are MFM.

On an IBM PC-AT, 250 KHz 300 RPM-written media is accessed at 360 RPM using
a 300 KHz clock.

TEAC FD55GFV/GFR drives can be selected at either speed.  In the DECmate III+
the drive is permanently slowed to 300 RPM to replace the similar RX50.  In
other applications it's left at 360 RPM.  There exists a PC option called
Compaticard that can change the speed as needed.

In some machines, the speed is varied using unusual drives.  This is used to
create "zones" on the disk, thus there are a variable number of sectors on a
track.  The Victor 9000 is an example of such a machine.  Most drive aren't
capable of this many steps of speed, etc. and the drives are essentially
custom models.

cjl