FDC Gap Length?

Dave Dunfield dave04a at dunfield.com
Sun Jul 17 10:10:29 CDT 2005

Hi Tim,

>Part of the calculation is the time it takes the data separator to re-sync
>after each gap.  Now, a "true" 765 doesn't have a data separator so maybe
>they leave this out.  It's also true that this number ought to be nearly
>constant depending on sector sizes.

I would assume this is covered by the minimum requirement that Allison was
talking about... Right now I am just trying to find the correct gap sizes
for formatting. Then I will have to worry about the gap size for writing
(which is different, as you obviously don't want to carry through to the
beginning of the next sector).

>Do you have the Intel 8272 data sheet?  (This was Intel's part number
>for their 765 clone.  It may not just be a clone but the exact same
>mask...).  IIRC there are more details/examples/math in the 8272 data
>sheet, including some recommendations for data separators and the good/bad
>of different types.

I do have the Intel data sheet and application notes, however they do not
provide any additional information on selecting the Gap size - just the same
"magic table" that NEC provides.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Collector of vintage computing equipment:

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