Path: utzoo!attcan!uunet!samsung!uakari.primate.wisc.edu!xanth!mcnc!ncsuvx!ecemwl!jnh
From: jnh@ecemwl.ncsu.edu (Joseph N. Hall)
Newsgroups: comp.sys.mac
Subject: Re: Quantum ROM fix report
Message-ID: <4601@ncsuvx.ncsu.edu>
Date: 21 Nov 89 05:58:38 GMT
References: <14618@well.UUCP> <9323@batcomputer.tn.cornell.edu> <788@wet.UUCP>
Sender: news@ncsuvx.ncsu.edu
Reply-To: jnh@ecemwl.UUCP (Joseph N. Hall)
Organization: North Carolina State University
Lines: 38

In article <788@wet.UUCP> tempest@wet.UUCP (Ken Lui) writes:
>In article <9323@batcomputer.tn.cornell.edu> eacj@tcgould.tn.cornell.edu (Julian Vrieslander) writes:
>>I do notice that the drive will occasionally exercize its swing arm when
>>there is no read/write going on....
>
>...my guess is that it reads the "next" piece of data from the drive
>and stores it in the cache.

Pray tell, what exactly is the "next" piece of data from the drive?  Does
the drive analyze the contents of the computer's memory while it idles
to determine what data is about to be read?  Or does it use some sort of
tachyon delay line to read the future in a more straightforward way?

The only sensible caching schemes that can be implemented by a drive without
cooperation from the host are those that cache previously-read, frequently-
read, and/or adjacent sectors (i.e., might as well read the whole track
anyway on the assumption it will all get used eventually).  Your drive could
be put to much more efficient use if it were used in a multitasking
environment and managed by a real disk controller; however you shouldn't
expect anything too subtle from a "dumb" caching drive.  A lot of this
effort is obviated by, for example, the Mac's own RAM cache and the Resource
Manager, which do the same thing but in a more directed, productive
fashion.

>Or so the tech support says who sold me my 105S.

Uh huh.

Although I'm ignorant on the exact details of the latest bunch of Quantum
drives, it sounds as if they now try to prevent various forms of "stiction"
by keeping all the possibly sticky parts moving ...  I'm sure what they're
doing is "within spec," and not detrimental to the drive in the long-term,
but then again they ARE the folks who write up and test against the specs ...

v   v sssss|| joseph hall                      || 4116 Brewster Drive
 v v s   s || jnh@ecemwl.ncsu.edu (Internet)   || Raleigh, NC  27606
  v   sss  || SP Software/CAD Tool Developer, Mac Hacker and Keyboardist
-----------|| Disclaimer: NCSU may not share my views, but is welcome to.