vote@octopus.UUCP (Pete Holzmann) (05/16/88)
In article <8769@iuvax.cs.indiana.edu> bobmon@iuvax.UUCP (RAMontante) writes: >This is a vote of appreciation for articles like this. Pete Hol(which is this? >sman or zberg?) posted a question about the appropriateness of such a thing; Well, it was Holzmann (and I think the other name is Holsberg :-) Thanks! >And sure enough -- I looked all through the product specification for my ST-238 >and there's nary a word about "window margins". Considering that it specifies >neato stuff like: > Recording Density 14,740 BPI > Flux Density 9,827 FCI This info is basically useless: it is the same for all MFM/RLL drives! >Something else you're surely dying to know: when Seagate says 65ms average >maximum seek time, that's for a 205-track (1/3 stroke) seek, average of an >inward seek and an outward seek, using buffered seek pulses. The full stroke, >innermost to outermost, is 150ms max. Track-to-track is 20ms max. One seek >error per million seeks; one recoverable read error per 10 billion bits read, >one NONrecoverable read error per trillion bits... > >So make sure you press your salesman closely on these specs! The Industry Standard way of measuring 'average seek' time is to measure a 1/3 stroke seek. Lots of PC programs measure something else, that's why they don't come up with the same number that the mfg does. (Note that in many cases, the published avg seek specs are very conservative and may not reflect the latest engineering improvements. Maxtor went to a mass-balanced head assembly in their rev 2 drives several years ago; average seek went from 30 to 24 ms, but the published marketing glossies didn't change!) Note that while average seek is important, track-to-track is even MORE important! 20ms is a really *gross* value for track to track; that's more than an entire revolution (16ms) of the disk! Pete -- OOO __| ___ Peter Holzmann, Octopus Enterprises OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014 OOOOO \___/ UUCP: {hpda,pyramid}!octopus!pete ___| \_____ Phone: 408/996-7746