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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.micro.68k,net.micro.pc
Subject: Re: all sorts of things + Intel processors vs. Motorola processors
Message-ID: <5674@utzoo.UUCP>
Date: Thu, 6-Jun-85 12:31:34 EDT
Article-I.D.: utzoo.5674
Posted: Thu Jun  6 12:31:34 1985
Date-Received: Thu, 6-Jun-85 12:31:34 EDT
References: <344@osu-eddie.UUCP>, <600@intelca.UUCP>
Organization: U of Toronto Zoology
Lines: 18

> ...  I believe
> Mot uses a two level microcode in the 68k and its followons...
> (can someone verify this?)

Yup, that's correct.  Don't know how it affects the speed.  Remember that
microcode fetch time normally is pipelined out, since the execution of
microcode is predictable (barring bizarre architectures with micro-
interrupts) and techniques like delayed branches are routine.

> ...this was one reason Zilog presented way back when for the performance
> of the Z8000 (they said it was good).

It's also one reason why the (hardwired) Z8000 took a lot longer to debug
than the (microcoded) 68000.  I believe Zilog has since admitted that not
using microprogramming was a mistake.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry