Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!isis!ico!rcd From: rcd@ico.isc.com (Dick Dunn) Newsgroups: comp.arch Subject: Re: disk rotation speed Summary: dual actuators: mechanics are tough Message-ID: <1990Aug3.203151.19320@ico.isc.com> Date: 3 Aug 90 20:31:51 GMT References: <2635@mindlink.UUCP> <10048@pt.cs.cmu.edu> Organization: Interactive Systems Corporation, Boulder, CO Lines: 30 (I wrote) > > [ ... ] In fact, you can see some high-end drives > > designed with dual actuators to reduce rotational latency... wayne@dsndata.uucp (Wayne Schlitt) asked: > I have wondered about this for a long time. Are there many drives > with more than one actuators? Why arent there more? 1. As I pointed out, it's expensive...you need two of a lot of stuff. That rules it out for low-end ("commodity" market) drives. 2. It takes more room. Small drives are up against their form factors; it's hard to find a place to put a second actuator. 3. It gives you a nonstandard interface. If you do it, you either have to make a controller that's smart enough to take advantage of it (which, at first blush, sounds tough to me), sell enough to get people to support it, or create and sell the driver-level support yourself. 4. The mechanical aspects are tough. You have to make things solid enough that having one actuator moving doesn't drag the other one off-track. This takes some careful isolation. Watch a busy PC-class machine some time, and note how the motion of the actuator in its little drive can make the entire machine move back and forth a few millimeters. Now consider that track spacing is down in the 20-micron range...and remember that you have to be a lot closer than that to stay "on track." (You're trying to stay in your lane, where 20 microns constitutes a complete lane change.) -- Dick Dunn rcd@ico.isc.com -or- ico!rcd (303)449-2870 ...Are you making this up as you go along?