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From: freed@aum.UUCP (Erik Freed)
Newsgroups: net.arch,net.micro.68k
Subject: Re: Asynchronous State machines
Message-ID: <404@aum.UUCP>
Date: Thu, 21-Nov-85 11:18:10 EST
Article-I.D.: aum.404
Posted: Thu Nov 21 11:18:10 1985
Date-Received: Sun, 24-Nov-85 07:23:20 EST
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Organization: The Aurora Systems Bunch
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Xref: watmath net.arch:2146 net.micro.68k:1359

> > Say, Henry, perhaps you should explain what you mean when you say
> > you've done the math and synchronous state machines can be run faster
> > than 50 nS?
> 
> I mean, specifically, that I have done the metastability calculations.
> Yes, I know about the issue.  My calculations were based on the formulae
> that accompanied the table in IEEE Transaction on Computers (I think it
> was) a while ago, and the data in the table, and a hefty safety margin.
> 
> > For something reasonable like once every 40 years at say a 1 MHz rate,
> > I recall a device like a S FF would take 70-80 nS. I understand the
> > new F logic settles faster and that may be the origin of the 50 nS
> > number quoted.
> 
> I don't remember the time needed for STTL, since in my opinion nobody in
> his right mind uses STTL now that FTTL is available.  FTTL does indeed
> settle faster.  Note the relationship between settling time and synchronizer
> performance is *not* linear.  FTTL is not just better, it is lots better.

Henry,
	I have this feeling that it is probably time for us to see your math
It feel that you are being overly optimistic about these times. It seems that
more than one person has come up with rather different figures than you.
-- 
-------------------------------------------------------------------------------
                           Erik James Freed
			   Aurora Systems
			   San Francisco, CA
			   {dual,ptsfa}!aum!freed