Re: Did Commodore cheat with the quad density floppies?

----- Original Message ----- 
From: "Mia Magnusson" <mia@plea.se>
To: <cbm-hackers@musoftware.de>
Sent: Tuesday, January 08, 2019 12:24 PM
Subject: Re: Did Commodore cheat with the quad density floppies?
 
>> 5.25" HD drives normally run at 360RPM; many have an option to select
>> 300 RPM, but compatibility with DD and QD disks is usually achieved
>> by changing the transfer rate instead.
> 
> The 360 rpm on those drives must had been to make them more of a
> drop-in replacement for 8" drives. 

That, and to use the same format across all drive types; by the time 3.5" drives came along compatibility with 8" drives would not have been a big issue, especially in the MS-DOS (semi-)compatible world.

But yes, 5.25" HD drives are indeed a drop-in replacement for 8" drives and often used as such these days when 8" drives and disks are getting scarce; 3.5" less so because of the need to change the speed, but dual-speed drives are still sought after by CP/M folks who prefer 3.5 to 5.25.