Path: utzoo!attcan!uunet!labrea!rutgers!tut.cis.ohio-state.edu!osu-cis!att!mtunb!jcm
From: jcm@mtunb.ATT.COM (was-John McMillan)
Newsgroups: unix-pc.general
Subject: Re: Floating Point ... Again
Keywords: MC68881, FPU, 68000
Message-ID: <1438@mtunb.ATT.COM>
Date: 15 Mar 89 02:11:26 GMT
References: <499@Portia.Stanford.EDU> <11170@s.ms.uky.edu> <4439@cbnews.ATT.COM> <296@carroll1.UUCP> <1429@mtunb.ATT.COM> <494@uncle.UUCP>
Organization: AT&T ISL Middletown NJ USA
Lines: 99

In article <494@uncle.UUCP> jbm@uncle.UUCP (John B. Milton) writes:
>In article <1429@mtunb.ATT.COM> jcm@mtunb.UUCP (John McMillan) writes:
>>In article <296@carroll1.UUCP> dnewton@carroll1.UUCP (Dave Newton) writes:

>>>The 68010 has a built-in MMU (Memory Management Unit) which is vital to
>>>the UNIXpc's multi-tasking operation.

>>Please so inform Motorola: They've yet to realize this!
>ya ba dee yub
 ^^^^^^^^^^^^^ -- ?  Since my statement was and IS correct -- Motorola
	has never claimed to have a built-in MMU in the 68010 -- I
	remain curious as to the precise translation of your wit ?-)

>>Their documentation is stupid enough to suggest they SUPPORT virtual
>>	memory (page faults, etc.) with improved restarts in the 68010.
>>	(I'm not sure one couldn't do the same with a 68000 -- given
>>	the ungodsly effort I've seen for Z8000 instruction-restart --
>>	but it wouldn't be pretty!-)

>They did a very good job, considering.

	I agree: I was saying WHAT MOTOROLA PUBLISHES & DOES --
	as opposed to the previous submitter's MISINFORMING people about
	what they do!

	"SUPPORT" is a capital idea; "built-in" is an overstated case.
	More Sloowwwllllyyyyy:  The first point I was making was that
	Motorola documents their 68010 processor as one which
		S U P P O R T S   V i r t u a l   M e m o r y.
	{Thanks for the spacing clues %-}

>>I'd recommend using the OFF-chip MMU that the 3B1 comes with, and which,
>>	alas, limits the 3B1 to 4MB VM.  And which EXISTS, if that's of concern.

>Yes, for THIS machine I would. Although having to copy the portion of the
	  ^^^^-Uh... THIS machine was the THE CONTEXT of the original Q&A.
		Floating Point assistance for the 3B1....
>mapping memory for a given process in and out with every context switch is
>time consuming, it was more than worth the alternative when this machine
>was designed. Now that big, high speed static RAMs are becoming available, I
>could see this method taken even further.

	(I'd recommend, say, Pittsburgh.)

>>>					Switching it for a 68000 would indeed
>>>be very bad.
>>         ^^^
>Not really fatal, if you have TWO 68000s.

	Maybe there's room on your disk expansion board;-}  If not, it's
	probably irrelevant to the discussion of FPA on the 3B1.  But
	it IS interesting!  (Not that THIS mortal grasps the instruction
	re-start mechanism therein... but it might be unnecessary?)

	But, back to CONTEXT -- it would be FATAL to any extent 3B1 software
				============================================
	to replace the 3B1's 68010 with a 68000!  Period!

>>"Fatal", yes.  Bad?  Thats a moral or ethical decision.  (Unless you're a
>>	politician where such things are NOPs.)

>Hmm, ok.
	Ooo ooohhhhh!  An agreement??????  (Naw.... just a typo, fur shur!)

>>Everyone is CAPABLE of submitting answers or statements:
				    ^^^^^^^^^^^^^^^^^^^^^
>>	1) Recognize your limits and
>>	2) try to exercise more courtesy -- like reading to the end of the
>>		news listings to see if others have posted replies.

>The only way people LEARN is by asking questions. At first stupid maybe,
>questions anyway. Many wonderful things have come from some "uninformed"
>person asking what appears to be a stupid question.
>
>        **** D O N ' T   F L A M E ,   I N F O R M ****

	An admirable motto.
		(But, I'd feel hurt if I thought JBM was referring to ME!)
	I didn't flame a QUESTION -- I flamed an ANSWER that was posted
	NOT by anyone who has familiarity with the subject, but by
	someone who was smitten by an urge to help -- regardless
	(1) of their limited familiarity with the subject and (2) the answers
	that had been submitted well before their posting.

	There is ample reason to believe some people LEARN by mis-answering
	questions.  Indeed, many wonderful things have come from some
	"un-informed" Bozo answering an honest question with a honestly
	half-wit reply -- I do it regularly!  (But I'd recommend
	practicing this in the closet for awhile before coming-out....)

	(dnewton: I'm calling ME not YOU a Bozo!  You'll have to
	work on it awhile to get past being just over-enthusiastic.)

I don't believe in these windy, broadly posted, negligibly informative
drivelings!  Had JBM sent a memo to me, or had he appeared better focussed
on my general insanity I'd have dropped it.  Which I do now, with no
more follow-ups on it from here!

j mcmillan	-- att!dev!null