Olivetti M20

On 5/18/2006 at 7:13 AM dwight elvey wrote: Not exactly--if you step between (according to the spec sheet) 5 and 500 usec, the drive treats it as a buffered seek request. Above that time, it tries to step at the rate you give it. AFAIK, only the original ST506 (and clones) required unbuffered seek. By the time the ST412 came out (long before the PC XT), buffered seek was the norm. It makes sense to use buffered seek as the drive electronics can make use of the ballistic nature of the seek mechanism (Newton's first law). A small almost-on-topic story here. When my wife bought her PC, PC-XT Taiwanese clones were just starting to make the appearance. The outfit she bought it from advertised "free hard disk and controller with purchase". It was a Xebec controller all right (nothing wrong with that), but a brand stinkin' new ST506--which the firmware on the Xebec wouldn't drive because of the unbuffered seek. Fortunately, it was a simple EPROM change (the Xebec COULD perform a 3 msec seek, it just didn't have that in its DPT). I've still got the 506, BTW, but the clone is long gone. But yeah, the 251 is definitely a buffered seek drive and you should use that capability if you can. Fire out your seek request with somewhere around 100 usec pulses, the drive will count them and then perform the seek, setting SEEK COMPLETE when done. And it will be quieter, too. Cheers, Chuck