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From: c60b-1eq@e260-1d.berkeley.edu (Noam Mendelson)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Comparing 486 to 386 Systems
Message-ID: <1991Apr6.045408.15395@agate.berkeley.edu>
Date: 6 Apr 91 04:54:08 GMT
References: <1991Apr4.142742.20601@lonex.radc.af.mil> <1991Apr4.204923.29300@agate.berkeley.edu> <27865@neptune.inf.ethz.ch>
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In article <27865@neptune.inf.ethz.ch> brandis@inf.ethz.ch (Marc Brandis) writes:
>In article <1991Apr4.204923.29300@agate.berkeley.edu> c60b-1eq@web-1c.berkeley.edu (Noam Mendelson) writes:
>>Most people also subscribe to the notion that if the number is higher it's
>>necessarily much more powerful, where in fact:
>>		(486 - 386) < (286 - 86) << (386 - 286).
>Well, I guess you subscribe to a similar notion which is also wrong, like most
>performance comparisons that oversimplify. In fact, (386-286) is the smallest
                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^
>of the differences, not by far the largest as your relation indicates. Give
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>me any instruction on the 386 except multiplies that are faster than on the 
>286.  I know you will not find one.

My comparison was of features, not speed.  The difference between the
386 and the 286 is vast.  The 386 is 32-bit while the 286 is 16-bit.
The 386 can split itself into four concurrent 8086's, each with their
own 1M memory space, thereby allowing true multitasking.  And the 386
can access a 4G address space, while the 286 is limited to a mere 16M.
The 286's main advantage over the 86 is its ability to map 16M of
extended memory.  Therefore, I reason that (386 - 286) >> (286 - 86).
The 486's main advantage over the 386 is the built-in math coprocessor.
However, this is somewhat of a null feature because it just saves
you some money and some space on the motherboard.  That is why I reason
that it is the smallest difference.

>Of course, I am comparing apples to apples and oranges to oranges,
>namely CPUs running in the same mode at the same clock frequency.

What you are comparing is apples to oranges.  The 386 is a 32-bit processor
while the 286 is a 16-bit processor.  It is in a different league altogether.

>While it is true that the 486 is not that much faster than the 386 on non-fp
>code running 16-bit software, you should see a larger difference running 
>32-bit code.

Perhaps, but since the majority of MSDOS software contains 16-bit code,
the 486 does not offer much realistic speed improvement.

+==========================================================================+
| Noam Mendelson   ..!agate!ucbvax!web!c60b-1eq | "I haven't lost my mind, |
| c60b-1eq@web.Berkeley.EDU                     |  it's backed up on tape  |
| University of California at Berkeley          |  somewhere."             |