8" disk drive questions...

[geneb]

On Sun, 31 Oct 2021, Chuck Guzis via cctalk wrote:

> On 10/31/21 9:57 AM, geneb via cctalk wrote:
>>
>> I'm working with the developer of the Applesauce disk imaging tool in
>> order to iron out some issues with 8" disk support.
>>
>> I'm using a Qumetrak 842 disk drive that's got support for both double
>> and single-sided media.  This means that it's equipped with two index
>> hole sensors, slightly offset from one another.  It's my understanding
>> that single-sided media has the index hole in one spot on the jacket,
>> and double-sided media has one in a slightly different location.
>>
>> The issue at hand is some NIB Dysan double-sided 8" media I have - the
>> disks have index holes in the jacket in both locations.  Is this
>> typical, or do I have some weird "special" disks on my hands?  The
>> Applesauce author posits that the combination of the dual-sensor drive
>> and the dual-hole media wouldn't typically find themselves together.  Is
>> this accurate?  If it's not, how would a system contemporary with the
>> media have handled the two index holes?
>
> Gene, are you certain that these aren't "flippy disks" (two index
> apertures)?
>
Chuck, here's a photo of the disk type I'm using:
https://i.imgur.com/Cq778xT.jpg

As you can see, they're not mirrored for "flippy" use.

> But I've seen what you describe.
>
> I recall one occasion where I received the single-double type that you
> describe and having to cover the single-sided hole to get to the other
> side of the disk.

If I have to mask off one of the index holes I can do that.  I can 
understand why Dysan would produce a disk that could be used in either 
drive, but a drive that could use both single and double-sided media had 
to have been common back then, which leaves me wondering how it was 
handled.

tnx!

g.


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