[Duo2400] Re: 2400 heat & speed

[Gregg Eshelman]

--- Dan K <macdan at comcast.net> wrote:

> Gregg . . . you seem to be saying hard disk drives
> use 
> _external_to_internal_to_external_ airflow as a
> major part of their overall cooling mechanism.

Not for cooling at all, but they do need to keep the
internal temperature at or below a certain value
(which of course is different for different brands
and models) to ensure that the heads can fly.

The drives with such venting have filters or long and
twisty intake passages to keep dirt out. The faster
drives that run hotter often have a lable near a small
hole on the top that says DO NOT COVER HOLE. If you
don't see any vent hole then there probably isn't one,
the drive is probably designed to run cool enough in
the environments it's expected to be used in or is
built to tolerate high heat with a fairly well
sealed case. I have a pair of fast SCSI II 1gig IBM
drives with winding air intake passages visible
under a clear lable. All three of the IDE drives
in my PC have holes on the top that are labled do
not cover. Some dead drives I've taken apart have had
"catch filters" near the edge of the platters to
trap and hold any small particles that might get
inside so they won't be "rattling around" inside.

Many ways to build a hard drive!

Today's drives are built to such exacting tolerances
that Maxtor doubled the capacity of one model "simply"
by adjusting the tension on the head support arms to
fly the heads one half-millionth of an inch closer to
the platters, along with firmware changes to
read/write the higher number of tracks.

My very first hard drive was a 5 megabyte, 5.25" full
height Tandon MFM type, in an IBM model 5150 PC.
At first it wouldn't do anything, not even spin up.
Then I noticed that the external head position
sensor arm was not in the position to block the
sensor.
(It used a stepper motor like a floppy drive instead
of the coil and magnets modern drives use.)
So I did the obvious thing, I grabbed the arm and
moved
it to the "home" position then turned the PC on.
The drive spun up and from then on worked fine. :)
Smart firmware programming! The parked sensor was
not blocked so the drive controller couldn't tell
where the heads were at power up, so to prevent
possible damage it was programmed to do nothing at
all.

=====
"When you are wrestling for possession of a sword, the man with the handle always wins." Hiro Protagonist

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