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From: steiny@idsvax.UUCP (Don Steiny)
Newsgroups: net.arch,net.lang.c,net.micro,net.micro.pc,net.micro.68k
Subject: Re: Re: Re: Need 286 "C" benchmark
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Date: Wed, 29-May-85 22:19:10 EDT
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Posted: Wed May 29 22:19:10 1985
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**

	Saying that it is unfair to compare the 286 with other chips
because there is no huge model compiler is begging the question.
Why are there no huge model compilers for the 286 even though
many people have been working on it for years?   Simple, the
286 is a nightmare for compiler writers.   There are no
truely general purpose registers in Intel chips.  The memory
management scheme requires the load a segement discriptor
table to get the information about the segments so that 
the program can get the data from the segment.   Note that
after the program has the information from the segment 
discriptor table, it still had to compute the offset in 
the normal Intel fashion.  Though the segmented Intel
chips have traditionally been difficult to write
compilers for, the 286 is even worse.  

	I was working on some the initial design of the compiler
for the AT&T sanctioned port to the 286 as a consultant to DRI.
We were having a meeting to discuss the global portions of the
the compiler, symbol table, object format, and so on.  We were
going over the 286 to make sure we all understood it.  After a
few hours we all were incredulous.  Why?  We asked.  What would
motivate such insanity?   We figured that it must have some
properities that are especially appealing to engineers.  We 
were all software, so we did not appreciate it.

	I have been using a huge model compiler on a 16032 for
several months.   It is Tolerant System's 4.2 port to the 
16032.  It has System V shared memory in addition to the
normal 4.2 IPC.   There is no problem at all in declaring
shared memory segments of 4MB.    This is not new, National
Semiconductor Genix had huge model many years ago.
There are many huge model compilers for the 68k chips.  

	Blame it on Microsoft! :-)

	Intel is not inherently evil or anything.  They have been
trying to maintain compatability with their older chips.  I have
heard rumors that the 386 will have linear address space.  Now
if they would just give compiler writers a few extra registers
to evaluate expressions and computer memory locations . . .