Pinout for SED9421

On 11/26/2005 at 12:48 AM ard at p850ug1.demon.co.uk wrote: Micropolis drives were 30 ms. track-to-track. I believe they used a 4-step per track scheme. The last Micropolis 5.25" drive (with buffered seek) I have has a closed-loop tach belt-drive spindle motor. I've never verified it, but I suspect that with longer seeks, the stepping rate is sped up considerably. I recall fooling with the step rate on a paper-feed motor on a printer and discovering that once you've established direction, you can crank the stepping rate pretty far up. Try it before things really get moving and you're likely to find yourself stepping backwards. But you have a point about the speed. I've got some Siemens 8" drives that use leadscrew positioning and they do just fine at 8 msec. track-to-track. The drive PCB has an interesting 40 pin DIP with an MOS logo and a Micropolis house part number and hooked to a 2.0MHz crystal, probably a microcontroller. A heavy, power-hungry, beautifully constructed drive, but slow track-to-track. Probably very expensive and not cost-competitive with the other drives that were coming out. I recall that one bone of contention among 5.25 " manufacturers was the hub clamping mechanism on which Shugart claimed the patent rights. The Micropolis does not use the Shugart design--the "cone" is solid, not segmented. When the taut-band positionier 5.25" drives came out, our drive specialist did some tests using MPI and Tandon taut-band positioners and declared that they were good enough and much faster than the Micropolis. So we used both for a time, but eventually settled on Tandon, albeit with our own drive electronics--he didn't think much of the Tandon PCBs. Cheers, Chuck