Re: Commodore "Most Wanted" List

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Fri, 04 May 2012 21:47:07 +0200 Message-ID: <4FA4323B.2070608@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 05/04/2012 09:19 PM, Spiro Trikaliotis wrote:
> Hello,
>
> * On Thu, May 03, 2012 at 07:07:38PM +0200 Gerrit Heitsch wrote:
>> I thought a floppy rotates at 300 rpm and not at 360 rpm? That would
>> make it 5 rev / sec.
>
> It depends. Most PC floppy drives rotate at 360 rpm. For example, this
> is mentioned at http://www.oldskool.org/disk2fdi/525HDMOD.htm.

Yes, that's why a controller board that is supposed to work with them 
runs the controller chip not at 8 MHz for 5.25" DD but at 9.6MHz. Back 
when they used discrete crystals on the controller boards, you usually 
found a 16MHz and a 9.6MHz crystal there. 16MHz for HD (on 5.25" and 
3.5") and (divided by 2) for 3.5" DD (since those were 300rpm) and 
9.6MHz for DD on a 5.25" HD.

  Gerrit

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