Pinout for SED9421

[Chuck Guzis]

On 11/24/2005 at 8:45 PM ard at p850ug1.demon.co.uk wrote:

(taking a break between putting the turkey in the oven and making the
cranberry sauce)

>Are you sure the SED9421 is not a complete data seperator? The PCB I am 
>looking at (from an Epson PF10 drive unit) doesn't seem to have much else 
>around the 765 disk controller chip.

I was trying to interpret the Japanese comments--it's entirely possible
that the writer was simply drawing a parallel to the 9420, not saying that
the 9421 used  the 9420.

Has anyone noticed a significant performance difference between the PLL
type data separators (e.g. the WD1691/2143 combo) and the plain-Jane WD9216
digital ones?  I suspect that the PLL type is more tolerant of drive speed
variations, but that hardly matters all that much with modern drives.  I
don't recall finding a disk that failed to read on a generic 9216-equipped
FDC but read fine on the old IBM PC floppy board.

Cheers,
Chuck