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From: agn@cmu-cs-k.ARPA (Andreas Nowatzyk)
Newsgroups: net.micro
Subject: Re: ANOTHER 32-BIT MACHINE???  (L O N G)
Message-ID: <380@cmu-cs-k.ARPA>
Date: Sat, 27-Apr-85 15:01:09 EDT
Article-I.D.: cmu-cs-k.380
Posted: Sat Apr 27 15:01:09 1985
Date-Received: Mon, 29-Apr-85 14:29:58 EDT
References: <9254@brl-tgr.ARPA> <1549@watcgl.UUCP> <5355@utzoo.UUCP>
Organization: Carnegie-Mellon University, CS/RI
Lines: 40

Here are my 2 cent's worth of experience with the 8086 and 80286:

Machine: a top-of-the-line CAD workstation running large circuit
         design tools on large designs (say > 60K gates).

Old configuration: 8086 @ 10Mhz, 1 wait-sate for main memory via a
                   modified Multibus, 1.5 Mbyt RAM, 80 Mbyte Disk

after "upgrade":   80286 (unknown clock/wait states) with a high speed
		   data path to 1.75 Mbyte RAM (avoids Multibus), same disk

A benchmark of a representative cross-section of all commonly used tool
on a representative design (for us) was run on both configurations:
Old configuration: 6h 31min   after "upgrade": 4h 10min.

The "upgrade" occured mid-December '84 and until now, the vendor was not
able to have their software running without frequent and unavoidable system
crashes (that is you can't do anything but to wait for them to fix an other
bug). Most of these bugs come from the fact that the 8086 had no memory
management/protection and the 80286 MMU is now catching all the references
to illegal RAM locations that went unnoticed on the 8086. Because the code
is large, there are ton's of them. So much for compatibility.

The second source of problems and low performance is also directly related
to the poor 8086 architecture: the 64Kbyte segment limit causes lots of
restrictions to the data structures (say, only x names/page, y wires/bus or
z blocks/design). We ran into a lot of those limits without being limited by
the amount of memory in the machine. These address limitations also explain
why dozens of temporary files are used: While compiling a 60K gate design
(that is large for the system), a dozen temporary files were allocated to
hold various symbol tables etc: most of these files were only a few 10Kbyte
long and the total size of all would have fit into the free memory easily:
no wonder that it takes 12h to compile.

Bottom line: the 8086, 80186 and 80286 deserve no place in a discussion
about state of the art 32 bit processors, certainly not to establish
credit to the 80386.

  --  Andreas             Arpa:  Andreas.Nowatzyk@cmu-cs-k.arpa
                          usenet:   ...!seismo!cmu-cs-k!agn