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From: dcall@mithril.wr.tek.com (Dale Call)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Mac LC info
Message-ID: <6404@wrgate.WR.TEK.COM>
Date: 26 Jun 91 16:00:43 GMT
References: <13375@uwm.edu> <1991Jun26.150217.614@otago.ac.nz> <22439@duke.cs.duke.edu>
Sender: news@wrgate.WR.TEK.COM
Reply-To: dcall@amadeus.wr.tek.com
Organization: Tektronix, Inc.
Lines: 49


In article <22439@duke.cs.duke.edu>, tbd@neuro (Tristan Davies) writes:
|> 
|> In article <13375@uwm.edu>, pretzel@csd4.csd.uwm.edu (Daniel L Premetz) writes:
|> > 2.)  The LC is listed as having a 16MHz, 32-bit CPU.  32-bit what?  Data
|> > bus?  Address bus?  Is this thing more like a MSDOS 286, 386SX, or 386DX?
|> >
|> I have seen a lot of answers to this question, but I'm not sure the question
|> has really been answered.  Is it possible to compare the power of an LC to
|> the power of one of the IBMs?  If so, where does the LC (or any other Mac,
|> for that matter) rank in the IBM hierarchy? Is it like an AT? PS/2? '386?
|> Since I have an LC and several of my friends have IBMs (yes, they're still
|> my friends(^: ), I'm quite curious.
-- 

Some of you folks commenting about 68020's should read a data book sometime ...

The 68020 has 32 bit address AND data busses, with 32 bit registers, etc.  Apple
chose to connect the 68020 in the LC to 16 bit data bus, rather than the more
conventional 32 bit bus as a cost savings measure (only needs 2 8-bit SIMMS for
memory instead of 4, fewer connectors, etc).  This definitely reduces the speed of
the 68020 w.r.t. memory fetches (instructions and data).  But the '020 has a 256 byte
instruction cache, so small instruction loops will run entirely from the internal
cache, which is 32-bit.  Between the cache, faster instructions, real 32-bit multiply
& divide, and a few other miscellaneous features, the 16Mhz '020 works out to be
about 3 times faster (on a Mac instruction mix anyway) than a 8MHz 68000 (which is
what you find in the Mac Classic/SE/Plus).

Comparing an IBM PC architecture machine with it's Intel processor to a Mac with the
Motorola processors is hard.  The typical PC has a lot of architectural limitations
that prevent it from performing as well as it could, and the worst of these are the
640K memory limits and the slow 16bit ISA bus.  I find that my LC runs windowing SW
(Mac Finder, MS-Word) as fast or faster than most 25MHz 386 machines with VGA
displays running Windows 3.0.  The real evaluation is whether or not *your*
application runs fast enough for you.  I have a friend who found out that MS-Word
runs a lot faster on his Mac SE than on his 20MHz 386 w/VGA graphics.  Also the
quality of Mac software is an order of magnitude better than the stuff on the PC.

A very happy Mac LC owner, and former PC owner (still have to use them at work though
:-)).

Dale

 "Exterminate!  Exterminate!"

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