Dan wrote: > At 4:56 PM -0400 10/23/2008, Al Poulin wrote: >> And then there is another angle. An old tale (perhaps mythic?) was >> that once a hard drive has "worn in" in either the horizontal or >> vertical orientation, one should not change its original orientation >> to the other. What's up with that? > > Not mythic. And still a problem, but perhaps less of one with > today's (physically) smaller drives. > > Each set of heads is on an arm, whoze positioning is *critical* -- > the head has to line up exactly over the track, or it fails to read > or write the data correctly. It's done with a step motor and > springs. As the drive ages, metal fatigues. If you suddenly change > the gravitational orientation by 90 degrees, the amount of pressure > on the arm changes quite a bit! If the servo motor can no longer > compensate... > > - Dan.
They haven't used stepper motors for a LONG time, probably since most drives moved from 1/2 (1.5") to 1/3 (1") height drives. And they've never used springs in the head positioner that I've ever seen. They now use what are called "Voice Coil Positioner" motors. They function much like the voice coil in a speaker. More importantly the heads follow the individual track on the disk as opposed to putting the head at a fixed position as older drives did. This means that even if the track is not precisely circular the head will still follow it. -- Clark Martin Redwood City, CA, USA Macintosh / Internet Consulting "I'm a designated driver on the Information Super Highway" --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
