Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!apple!mips!lloyd!cprice
From: cprice@mips.COM (Charlie Price)
Newsgroups: comp.arch
Subject: Re: R4000 - compatibilty questions
Message-ID: <46081@mips.mips.COM>
Date: 21 Feb 91 19:12:55 GMT
References: <49041@apple.Apple.COM>
Sender: news@mips.COM
Reply-To: cprice@mips.COM (Charlie Price)
Organization: MIPS Computer Systems, Inc
Lines: 40

Yet again, hoping the net gods bless this posting...

In article <49041@apple.Apple.COM> baum@apple.UUCP (Allen Baum) writes:
>[]
>>In article <45792@mips.mips.COM> cprice@mips.COM (Charlie Price) writes:
>>Superscalar is pretty easy to define, but
>>what *does* superpipelining really mean?
>
> (details of R4000 pipe... Thanks!)

Ya Betcha!
By the way, this is the level of detail in information that
was handed out to the press.  You can look for pictures in
the glossy trade rags any time now.

>This actually runs contrary to MY definition of superpipelined, which
>is probably like MY definition of RISC - there's no such animal as THE
>definition...

While I agree that there is no "one true meaning",
for the term, we need *some* terminology we can agree on
to talk about these things.
I will have more to say on this in a subsequent posting.

>I would expect a multiple cycle hit for taken branches as well, without
>some kind of branch acceleration technique like a branch target cache.

Yes, increased load latency and branch latency is one of the effects 
of increasing the pipeline depth.  This is a non-negligible
consideration in picking a pipeline structure.

>I'm also curious about the compatibility provisions.
>Inquiring minds would, of course, like to know. Is this level of detail
>still subject to non-disclosure?

I can't find any discussion of this in our technology presentations,
so this will have to be a topic for the future.
-- 
Charlie Price    cprice@mips.mips.com        (408) 720-1700
MIPS Computer Systems / 928 Arques Ave. / Sunnyvale, CA   94086-23650


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