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Path: utzoo!watmath!clyde!rutgers!sri-spam!ames!amdahl!drivax!holloway
From: holloway@drivax.UUCP
Newsgroups: comp.sys.m68k
Subject: Re: move sr/move ccr: is bigger better?
Message-ID: <862@drivax.UUCP>
Date: Mon, 2-Feb-87 13:31:25 EST
Article-I.D.: drivax.862
Posted: Mon Feb  2 13:31:25 1987
Date-Received: Tue, 3-Feb-87 22:10:57 EST
References: <809@imagen.UUCP> <561@elmgate.UUCP> <1090@msudoc.UUCP>
Reply-To: holloway@drivax.UUCP (Bruce Holloway)
Distribution: world
Organization: We Can Build You, Inc.
Lines: 30
Keywords: logic? CCR Protection Memory Management

In article <1090@msudoc.UUCP> conklin@msudoc.UUCP (Terry Conklin) writes:
>           "What is the difference between the 68000,the 68010
>and the 68020? And throw in 68030 for good looks."

The 68008 has an eight-bit data bus, but is otherwise identical to the 68000,
which has a 16-bit data bus. The 68000 cannot recover from address and bus
errors, which means that paging schemes which depend upon the ability to
recover from bus errors won't work.

The 68010 saves enough info on the stack to recover from bus errors, and even
tell you where and how they happen, and allows you to complete the instruction
with some of your own hardware, talk to an MMU, etc. (Address errors, too. It
is possible to write an interrupt handler to allow you to access words on odd
byte boundaries, for example). So the big 68010 difference is, it allows you
to add an external MMU for dynamic paging schemes. (It is also somewhat faster,
and allows pipeline optimization).

The 68020 does all this, and more. It has instruction cacheing, which means
that for short loops, the 68020 needs never go to the external memory for the
code. It also has a very slick interface to co-processors, like floating point
chips and and MMUs (which are still external). The 68020 is a lot faster than
any of the previous generations.

From what I hear, the 68030 will have expanded caches, plus, possibly, data
cacheing.

-- 
....!ucbvax!hplabs!amdahl!drivax!holloway
My balogna has a first name, it's Jimbob. My balogna has a second name, it's
Boltwangle. But it prefers to be called Jim.