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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: Q. why 5400 and 7200 rpm disk drives?
Date: Thu, 10 Oct 2002 04:07:48 GMT
NNTP-Posting-Date: Wed, 09 Oct 2002 21:07:48 PDT
The little lost angel wrote:
> On 9 Oct 2002 18:32:39 -0700, Winfield Hill
> > Hmm, why did disk drive manufacturers settle on rotation speeds
> > like 5400 and 7200 rpm? These correspond to 90 and 120 rps, or
> I asked the same question some time back
> (Ignore the last part rant by Eric Gisin vs DrArm)
> I think the conclusion was something like it's easier to evolve from
> an existing design rather than trying to do something like a 8000RPM
> or 9000 RPM *shrugz*
There was some truth in that (hardly any really) until zoned bit
recoding came along. That meant nearly constant data density and pretty
much decoupled data rate from disk RPM. The data rate in zoned bit
recording varies with radius in zones. I can't remember all the numbers
of zones I have seen but maybe anywhere from 8 to 24. It really got
messy when they started optimizing data density for flying height,
linear velocity and head yaw angle.
I mentioned my first disk drive experience at DEC more than 20 years
ago. I needed a read channel for my 2850 RPM drive. I got a read channel
from a project doing a 3600 RPM drive with totally different heads (I
was using Winchester heads). It took a bit of diddling but I had the
read channel working at better than 1 error in 10^10 bits in just a few
days. That was a good goal back in 1980 because our Reed-Solomon code
could correct at least 1 error in 10^8 (codes used today correct 1 error
Without marketing, disk spin speeds would pretty much be driven by data
density and read channel speed. Note that way back when, a drive might
use a 3600 RPM motor but the spindle was quite often belt driven so the
speeds varied a lot. I didn't work on the DEC RA-8x series but it was
belt drive and I'll bet it ran around 3000 RPM.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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