naiman-1984-introduction-to-the-lisa

15
The Lisa's Hardware
Last but not least, Apple maintains a toll-free number
Lisa users can call with their questions, problems,
etc.-(800) 553-4000. Like most such numbers, sometimes
it's "temporarily busy." (Are there numbers that
are "permanently busy" Probably there are; I've certainly
come across some that seemed to be. But this
Apple number seems to be adequately staffed.)
Power
For all its ease of use, the Lisa is a very powerful personal
computer. Much of the reason for this is the CPU
chip it's built around-the Motorola 68000 microprocessor,
one of the most highly praised chips of recent years.
Unlike the eight-hit chips used in many personal
computers (which process data in eight-bit chunks), and
unlike the 8088, the 8/16-hit chip used in the IBM PC
and its imitators (which processes data in sixteen-bit
chunks internally but takes it in and sends it out eight
bits at a time), the 68000 is a 16/32-hit chip.
As you may have guessed from its name, a 16/32-
bit chip processes data 32 bits at a time, but takes it
in and sends it out 16 bits at a time. The biggest computers
in the world only process data 64 bits at a time,
and many computers that cost millions of dollars are
32-bit machines. So the Lisa is no slouch in terms of
raw computational power.
Unfortunately, the Lisa asks far too much of the
68000. Almost 40% of its time is spent simply dealing
with the screen, and this is compounded by the slowness
of the Profile, which is constantly being accessed.
This overloading of the 68000 (and overuse of the
Profile) makes the Lisa quite slow in many vital operations-in
spite of the fact that there are three other chips
to handle input/ output functions. Long delays in updating
the screen and sending data to the printer are the
result; this is the Lisa's single greatest failing. The Lisa
2 software is two to four times as fast, but even that
may not be enough; this is an area where the Lisa really
needs a lot of improvement.