Asri-unix.1178
net.works
utzoo!decvax!cca!sri-unix!DPR@MIT-XX
Wed Apr 7 07:27:30 1982
Hank Walker and Performance
Hank Walker's performance comments touched a nerve. "the only way to
compare architectures is in assembly language"? Pish tush. Let Hank
write all his programs in assembly language, then. No one
except hardware-only bigots has made that mistake for the last
10 years. If a salesman told me that I'd throw him out of my office.
It is true that better and worse compilers exist, and it may be true
that the VAX is wonderful when you have a good compiler. Show us.
On the other hand, Pratt in his comments never compares programs that
do a lot of I/O. Instruction set architecture has very little effect on
the performance of "REAL" programs (i.e. other than Puzzle). How fast
you can get data into and out of a machine is much more important.
The I/O bandwidth on most 68000 machines is pitiful. The VAX,
with its MASSBUS, and UNIBUS and cache memory, is a winner here, and
shows the real cost difference between big and little machines (the CPU
instruction interpreter is such a minor component of cost...)
Getting to a substantive point, we are just about to hook up a gaggle
of 750's to a local net, with the disk in some cases being provided by
a shared server across the 10MB net. So I think in a couple of months
we will have a data point for Pratt on this subject. I am unaware of
any useful comparisons and would be interested in other work.
I expect there to be little perceivable difference in UNIX on a 750
with local RK07 and UNIX on a 750 with remote simulated (admittedly we
will be using a faster disk for the remote server). As main memory gets
cheaper this is probably the way to go to keep your office quiet and your
disks reliable.
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