Substituting DSHD for DSDD disks (or DS2D if you prefer)

Eric Christopherson echristopherson at
Sat Oct 24 20:59:38 CDT 2015

I know Chuck Guzis has written about this, but I don't see that he's done
so publicly in the last few years, so I thought I'd ask here about his and
others' views on the perennial question of whether (some) 3.5" DSHD disks
can be reliably used in DSDD-only drives. The oft-repeated claim is that
writing can appear to work just fine, but that even a few months later read
errors will occur.

On <> Chuck was quoted
as (actually, correct me if I'm wrong -- it's a little hard to be sure this
was Chuck's words) as saying "Usually, they're just fine, with the error
rate approximately the same, whether or not 2D or HD media was used." Just
before that, he said  "I think that the overall quality of DSHD 3.5" media
isn't what it used to be, so that might contribute to the general
impression that 3.5" HD diskettes used as 2D aren't reliable. I have
problems enough finding reliable 3.5" DSHD floppies used as such." Chuck et
al., what's your feeling now, both on the overall reliability of HD disks
in DD drives, and on whether it depends on how recently the disks were

Elsewhere on the page (I don't recall now if it was Herb or Chuck that said
it) it was conjectured that HD disks that have never been formatted as HD,
-OR- disks that have gone through a good degaussing, will have better luck
retaining data. What does everyone think about this? And would an
electromagnetic library security system (the kind that's like a tube
through which checked-out materials are put; often with a caution not to
put tapes or floppies through it) be a suitable degausser?

        Eric Christopherson

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