From: KPJ (kpj@sics.se)
Date: Wed Sep 29 1999 - 03:10:16 MDT
It appears as if <ronkean@juno.com> wrote:
|
|Tapes are magnetic media, and tapes are rather slow, perhaps the slowest
|of all computer-related storage technologies. Hard disks (magnetic) and
|CD-ROMs (optical) are somewhat faster than tape, but much slower than
|volatile RAM (DRAM). There is a big operational difference between hard
|disks and CDs on the one hand and tape on the other, and that is that
|tape must be mechanically reeled to the spot where a read or write
|operation is required, so tape has a slow average access time for random
|access, very much slower than disk type geometry.
Mechanic devices (tapes, mechanic disk drives, CDs, etc.) require more time
to perform an operation than electrical or pure-magnetic devices do, as they
move _atoms_ around. A DRAM device moves _electrons_. Electrons require much
less power to move around, as they occupy less space, have much smaller mass,
and have a non-zero charge so one can use electrical fields to move them.
So if one compares mechanical devices to a DRAM device,
one, figuratively writing, compares apples and nuclear submarines.
Comparing various solid-state devices (like DRAMs and flash disks) make
more sense (the comparisons have greater information contents).
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