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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Disk drive handling in assembly
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Date: Sat, 05 Oct 2002 12:52:39 GMT
NNTP-Posting-Date: Sat, 05 Oct 2002 05:52:39 PDT
The little lost angel wrote:
> On Sat, 05 Oct 2002 02:52:36 GMT, Chuck Simmons
> >Yep. Back in the 14 inch days (when I jumped on board disk engineering),
> >some drives had a separate motor and the spindle was belt driven. The
> >head disk assembly got quite hot anyway. The motors used today are
> >usually pretty efficient brushless DC motors so the heat is from air
> >friction. These days I work in optical. I can spin at DVD 2X with maybe
> >100ma and DVD 10X at about 1 amp. The motor alone with no disk takes
> >about 50ma for DVD 10X. The difference is air friction.
> Hmm, since you're the expert on drives here, I've always wondered
> about something?
> Is it better to have a ROM drive that spins constantly say at 10x,
> compared to one that spins up to 50x, then after a minute or two,
> stops, then if you use it again, does another violent ramp up to 50x?
> In terms of which would probably last longer given similar parts?
> I've always suspected my current drives lasts a lot less than my first
> couple of 4x, 12x drives because back then they simply hummed along
> without all those spin up spin downs every half an hour or so.
I don't really know. I came from hard drive design and moved into
optical drive ASIC design and I don't see drive life data in that end of
the business. But CDROM and DVDROM are both read with constant linear
velocity meaning the drives have to change speed by more than a factor
of two from disk ID to disk OD. Thus a seek can involve a pretty big
change in speed anyway. I suppose thermal cycling of the spin power
driver could be a life concern when spinning all the way down and then
spinning up again. I use a spinup current of more than an amp from the
12 volts but that's just me. I haven't checked what commercially
available drives do.
A life issue I have seen is the lasers. We get our lab test mechanical
units with optics from customers. Out of a carton of 12 I got, the very
first unit I pulled out of the box had a bad DVD laser (the CD laser was
OK). I have a pile of about a dozen bad optical units on my bench all
with dead lasers and it is usually the DVD laser that blows. We don't
try to change lasers because the complete optical unit is quite cheap so
I replace it as a unit.
The optical game is new to me and it has some pretty tough challenges.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com
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