RE: Hard drive on the EPP

["John H. Kim" <jokim@mit.edu>]

In message Tue, 25 Oct 94 16:58:07 -0400,
  dewar@gnat.cs.nyu.edu (Robert Dewar)  writes:

> 500k/s - 1MB/s for disk transfer rate is very pessimistic. I have the 810
> meg disk on my 755C, and hibernation of 36 megs takes about 22 seconds.

Here's a quick chart based on the disk's physical specifications (sectors
per track i.e. sectors in one revolution, and rpm) based on the standard
512 byte sectors:

    kilobytes passing under disk head each second

            RPM   1800     3600     5400
   Sec/Trk ------------------------------
     17    |      255k     510k     765k
     33    |      495k     990k    1485k
     43    |      645k    1290k    1935k
     63    |      945k    1890k    2835k

Most of the older disks I know of are 33 sectors/track and 1800 rpm.
3600rpm disks started showing up in force a couple years ago, and 5400 rpm
disks are still pretty rare (usually advertised as optimized for
multimedia).  33 sectors/track seems to be the most popular.  You can
figure out the rest.  The rate on the chart is the FASTEST the drive can
read data off the disk - 1:1 interleave, data in sequential order on only
one track, no bad sectors, etc.  The drive can exceed this speed for a
fraction of a second via a cache hit, but the sustained data transfer rate
will not be much higher.

There are LOTS of drives with LOTS of different specs so don't take the
above chart as covering all drive types.  I have no idea what the specs on
the TP's hard drives are.
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John H. Kim        | "Mike Espy simply forgot he was no longer a Congressman."
jokim@mit.edu      | -anonymous, on the Secretary of Agriculture's resignation
jokim@uni.uiuc.edu | due to conflict of interest charges for accepting gifts.
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