5.25 drive with sector output

dwight elvey dkelvey at hotmail.com
Mon Dec 24 13:35:51 CST 2007





> From: cclist at sydex.com
>
---snip---
>>
> Most newer 3.5" drives subsume the "ready" circuit into a monolithic
> hunk of silicon with the rest of the drive control. Index output
> pulses are blocked until the period between indexes satisfies some
> internal "ready" standard. Also, 3.5" drives can have *very* wide
> index pulses when compared to 5.25" and 8" drives.
>
> Of course, any 5.25" drive with this logic (and it's very common)
> will view a hard-sector disk as not being anywhere near the correct
> speed, so will not only not come ready, but will block *all* index
> pulses going out.

 That is why I like the Qume. It has no monolithic chips. Just 14 and
16 pin dips. If needed, I can bypass any such circuits if needed
to get the ready signal.

>
> This feature has a curious implication if you decide to replace an
> older drive without the "block index until ready" logic with a newer
> drive with that logic. Many controllers (such as the WD1770) or
> software will count up a few sectors after select or motor on before
> commencing an operation. The result is that everything still works,
> but the latency after selecting a drive increases significantly.

 The double density controller uses a serial chip. I don't expect to
use the controller once I manage to get the floppies archived. I
have a single density system runnning fine on my 8813 now. My
main issue is to get the data from the disk.
Dwight


>
> Note that once the drive been selected and come ready, this is not an
> issue.
>
> For what it's worth,
> Chuck
>

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