Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucsd!ames!amdahl!kim
From: kim@uts.amdahl.com (Kim E. DeVaughn)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A3000 CPU slot
Message-ID: <29VY02MJa5P.01@amdahl.uts.amdahl.com>
Date: 8 May 90 10:09:53 GMT
References: <11207@cbmvax.commodore.com> <11378@cbmvax.commodore.com> <11413@cbmvax.commodore.com>
Distribution: comp
Organization: Amdahl Corporation,  Sunnyvale, CA 94086
Lines: 63

In article <11413@cbmvax.commodore.com>, valentin@cbmvax.commodore.com (Valentin Pepelea) writes:
> In article <72GN02gAa4MS01@amdahl.uts.amdahl.com> kim@uts.amdahl.com (I) wrote:
> >
> > Are you implying that Zorro3 now supports atomic read-write-update cycles now
> > (i.e., test-and-set, and similar operations)?
>
> Nowhere in my article did I imply such a thing, but yes, RMC (ream-modify-
> cycles) are supported on the Zorro III bus. Semaphore implementations for
> inter-processor synchronisation is thus simplified.

Well ... you did say you thought multiprocessing would be "a snap", and I
can't see how it'd be *easy* without atomic Test-and-Set capabilities.

I'm pleased to see that Zorro-III is supporting this, but couldn't this pose
a problem when s/w that does this is run on a Zorro-II machine, where the co-
processor chips can sneak-in in the middle of the read-modify-write cycle?

Or are you planning to have the OS handle this for the application, and "do
the right thing" depending on what kind of machine it's running on?


> > And what about cache coherency (I'm not up on 030 bus-snooping specs)?
>
> There are new functions in the Exec allowing you to flush the cache when
> necessary. Furthermore, some regions of memory are declared as non-cacheable.
> This is simple to implement using either hardware cache inhibition or
> software translation table inhibition.

So we'll have to depend on such applications and/or AmigaOS to be "well-
behaved" and ask the "other" CPU(s) to flush, if the access is going to be
made to a memory location that could be shared?  Is that correct?


Speaking of caches, does the A3000's SCSI-driver "do the right thing" and
flush the data cache(s), so one can run with the D-cache enabled without
worry now?


All this foresight sounds very positive for the future.  Good job y'all!!!

"Amiga ... the 1st *afordable* multiprocessing machine.  While other's are
 struggling to but implement multitasking!" ... I love it!   :-)


> > > I'm part of the Snap, Crackle and Pop group. :-)
> >
> >Is that different than the "poof!" group?  :-)
>
> Never heard of the "poof!" group, but you all now Capt. Crunch, don't you?

Hmmmmm ... "poof!" was the equivalent to "It's in there!" during the 1.2->1.3
upgrade timeframe (possibly before that).  I think it was Dave Haynie, or maybe
Andy Finkel who I first noticed using it.   As for "Crunch" ... did he ever
get his legal difficulties resolved ... anyone know ...?

/kim

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