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From: rex@cs.su.oz (Rex Di Bona)
Newsgroups: sci.electronics
Subject: Re: ECL logic computers ?
Message-ID: <2544@cluster.cs.su.oz.au>
Date: 26 Jun 91 22:48:41 GMT
Article-I.D.: cluster.2544
References: <7183@gara.une.oz.au>
Sender: news@cluster.cs.su.oz.au
Reply-To: rex@cluster.cs.su.oz (Rex Di Bona)
Organization: Basser Dept of Computer Science, University of Sydney, Australia
Lines: 29

In article <7183@gara.une.oz.au> rbennet1@gara.une.oz.au (Robert Bennetts) writes:
> Hi,
>     can anybody out there tell me why ECL logic is not used to construct
> computers (to my knowledge anyway)

It is. Some of the mainframes use it and the MIPS R6000 also uses it.
Why dont more people use it? Well, two reasons spring to mind. Even
having the CPU running fast you still need fast memory, and ECL ram
would cost, boy, would it cost. Also it would require massive power and
cooling.

The other reason is that CMOS is getting much faster. It was believe
that CMOS would run out of steam at (take your pick, 20, 30, 40, or
50MHz) at various times, but it still goes. You can buy a CMOS part
from Brooktree (a video DAC) that runs at up to 130Mhz or so, and I
have heard of a 200Mhz CMOS processor (DOD, but this might be an urban
myth :-)

So, the reason you don't see too many ECL machines out there is that
they would be a bigger headache to run, and cost MUCH more, and that
CMOS machines are catching up anyway! (The new HP snake machines, the
MIPS R4000 technology, and the RS6000 for example)

Also, when I was last designing chips (ages ago now) the design tools
knew much more about CMOS (and NMOS :-) than about ECL, so it was
easier to get that chip fabricated.
--------
Rex di Bona (rex@cs.su.oz.au)
Penguin Lust is NOT immoral