Path: utzoo!utgpu!attcan!lsuc!ecicrl!clewis
From: clewis@ecicrl.UUCP (Chris Lewis)
Newsgroups: comp.arch
Subject: Re: ETA-10: CMOS or ECL?
Message-ID: <126@ecicrl.UUCP>
Date: 22 Oct 88 19:25:42 GMT
References: <3539@phri.UUCP>
Reply-To: clewis@ecicrl.UUCP (Chris Lewis)
Organization: Elegant Communications Inc. (CRL Division)
Lines: 74

In article <3539@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>
>	I was at JVNC yesterday gaping through the plate-glass windows at
>the ETA-10 ...
>
>	At one point I said something like "The CPU is all ECL, right?",
>and he said, "No, it's CMOS".  This really surprised me.  Is it really
>CMOS?  I always thought of CMOS as pretty slow stuff, just pushing the
>speed of normal TTL, and certainly not supercomputer stuff.

Modern high-speed CMOS IC's are actually outstripping much of TTL.  For example,
I believe that the 74HC series is approximately the same speed as 74AS
(advanced schottky).  Coupled with the fact that it is possible to
create considerably denser CMOS than TTL you no longer have as much
capacitance to charge - capacitance is one of the determining factors
in CMOS speed.  CMOS has come a long way from the old RCA CD4000 series
parts...  To answer someone else's question which is connected:

In article <558@quintus.UUCP> Jabir Hussain (jabir@quintus.uucp) writes:

> could anyone tell me what ASIC stands for?  thanks

ASIC stands for "Application Specific Integrated Circuit".  Various
IC manufacturers have developed a process by which a customer designs
what he wants his ICs to do, and the IC manufacturer programs their
machinery and makes it.  Effectively, an ASIC part is a medium to large
gate array, where the final connections between each of the elements
can be easily rearranged as the last step in fabrication.  The customer
is often given some CAD software that knows the geometry and capacity
of an unprogrammed ASIC part, the customer builds his circuitry using
CAD and a library of "macros" which describe basic building blocks.
A tape of the result is sent to the foundry to be used in constructing
a mask for the final etching phase.  The chip is then encapsulated
and tested and shipped to the customer.  Usually costs something like
$30K to $100K to run through one iteration of CAD -> finished part.
[Not to mention running the CAD (though many manufacturers rent out
time on their own systems) and engineering costs]  Thus, you gotta
be real careful that you get it right the first time.  Many manufacturers
also supply simulators so you can test the heck out of it before
committing to silicon.

Think of it as an mask-ROM, where instead of programming ones and zeros,
you're programming connections between gates.

Now, some of the modern ASIC is pretty spectacular.  I believe that
the ETA-10 is built with a 6000-gate ASIC part, with gate delays
on the order of .2 to .5 nS.  Resulting in what a CDC person described
as "effectively a Cyber 205 on a board".  Something like 15ns cycle
time for the whole machine, as opposed to something around 7 for the 205.
Motorola has an 10K gate ASIC family (though, this is ECL I think) which
has gate delays of 60-100 pS!

The libraries are also pretty spectacular - some libraries come complete
with entire CPU's as basic building blocks.  You want multiple CPUs
on a single chip?  Easy!  Many PC/AT/386 clones rely upon
these parts for reducing their parts count: eg: Chips and Technology
as well as Zymos market chip sets (4-7 components) that replace most
of the 100 or so MSI parts required on a motherboard.   Zymos actually
built a single ASIC part that replaced *everything* on an AT motherboard
except for the CPU chip.  The only reason you don't see such things around
now, is that they figgered they'd need something like 300 pins, and
the yield would be lousy.  So it never went in production.  Many of the
new display adapters on PCs consist of a single ASIC part.   If I'm not
mistaken, IBM pioneered a lot of this technology in building their
big iron, and other manufacturers (eg: machine manufacturers like
CDC, or chip companies like TI, Motorola) have followed suit or 
independently developed their own ASIC fabrication and design process.
There are now companies exclusively doing ASIC or ASIC tools (C&T, Zymos, 
CDC has a subsidiary doing it, LSI etc).
-- 
Chris Lewis
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