Re: Did the Apple II use single-density 5.25" drives?

[David Schmidt <schmidtd@my-deja.com>]

On 6/6/2013 1:22 PM, slickrcbdnews@gmail.com wrote:
> I think I read somewhere that the Apple II's 5.25" drives could use single sided, single density disks just fine.

You read that Apple II drives can use single sided, double density disks 
just fine.  In terms of magnetic coatings, there really is only DD and HD.

> Was that true and that the "double density" aspect was wasted?

No, the "double sided" aspect was wasted unless you notch and flip. 
There was only a read head on the bottom of the Disk II drive.

> I also know that MS-DOS systems could use both sides simultaneously. Howver, what about the "single density" aspect?

Correct, other drive mechanisms had heads on both the top and bottom, so 
they could use both sides without flipping.  "Single density" really 
refers to the recording method (FM vs MFM).  Google for more.

> So, were they single density or double density drives?

Well, the drives use popularly named "double density" media - though the 
GCR encoding dictated by the Woz controller board didn't produce 
capacities as dense as possible relative to the media capability.  We're 
really talking about two different things here... recording scheme vs. 
track width.  Track width is, in media terms, either DD or HD.  (Other 
much less popular variants exist that I'm ignoring now.)

> [...] 400K disks were replaced with 800K disks on the Mac

That particular difference was only single-sided vs. double-sided.  Both 
drives used the same DD media.