Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]

Chuck Guzis cclist at sydex.com
Tue Jun 19 18:16:53 CDT 2007

On 19 Jun 2007 at 18:47, Ethan Dicks wrote:

> Commodore did vary the bit clock to create 4 zones of sectors on 5.25"
> floppies (2040/3040/4040/2031/1541/1571 for the PET, VIC-20, and
> C-64).

Yup, you're correct.  I was thinking of the C128/C64 GCR "zoned" 
drives.  But let's consdier the Amiga format and compare it to XDF.  
The 250Kb/sec capacity for a DS2D diskette is 6250 bytes.  So, 11*512 
= 5632 bytes, giving a track utilization of about 90%.  So XDF at 94% 
still beats the Amiga with all of its fancy hardware--and XDF uses 
standard gaps and address headers--and even puts an IAM on the track. 

The Amiga could have done the same thing with nothing more than a 
plain old 28-pin WD1770.


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