Early 3.5" Floppy Drives

[Chuck Guzis]

On 12/16/2005 at 12:49 AM ard at p850ug1.demon.co.uk wrote:

>> Any PC controller that can do 720k 3.5" format can do 
>> 8" as it's the same data rate.  it's not what chips was 
>
>I don;'t think you mean that!. The 720K 3.5" format is the same data rate 
>as the 360K 5.25" format. You mean any controller that can do the 1.44M 
>3.5" format (or for that matter the 1.2M 5.25" format), surely. Those are 
>the same as the 8" data rate.

Yeah, he did--sort of.  This assumes that the data separator can be
jiggered to deliver separated FM data at the same rate that it delivers
3.5" separated MFM data.   i.e., 8" FM has the same data rate as 720K 3.5"
MFM.

Although, I'm still puzzling over my databook's definition of pin 21, it
says "500 KHz for FM and 1 MHz for MFM" but makes no mention of write data
rate (i.e. mimifloppy vs. 8").   Could this be simply something left out?

Cheers,
Chuck