Re: [colorforth] Intellasys question for Jeff Fox

[John Drake <jmdrake_98@xxxxxxxxx>]

----- Original Message ----
From: "gwenhwyfaer@xxxxxxxxx" <gwenhwyfaer@xxxxxxxxx>
To: colorforth@xxxxxxxxxxxxxxxxxx
Sent: Saturday, May 24, 2008 1:32:32 PM
Subject: Re: [colorforth] Intellasys question for Jeff Fox

On 24/05/2008, Jeff Fox <fox@xxxxxxxxxxxxxxxxxxx> wrote:
>> In this case both machines provide machine precision.

> You repeat this later, but I can't help thinking it's an evasion. Most
> people, when they want to know precision, are thinking of a number of
> binary digits. (And a word about accuracy wouldn't go amiss either.)
> Since the F21 had a 21-bit word, would it be fair to assume that the
> precision was 20-bit? What about accuracy?

Nonsense.  Machine precision for a 386 is obviously up to 32 bits.
Machine precision for an F21 would be 20 bits.  No "evasion".
The key issue for the sake of comparison is if any the precision
requirements would be such as to cause you to need to do
double word operations on the F21.  If all you need is say 16
bits than that could be done on the F21 the 386 or even the
C18.  For the record a recent (2 years ago) 16 bit implementation
of CORDIC was posted on comp.lang.forth.

http://www.complang.tuwien.ac.at/forth/programs/cordic.fs

So if anyone REALLY cares about benchmarks (I don't) they
can run this on their favorite Intel chip and look at the comparisons
for the c18 whenever that library is released.

>> Of course F21 was designed for parallelism and a fair
>> comparison on power or cost or transitor count means
>> we should be comparing 100 F21 to a 386/387 combination.

> What was the cheapest that single F21 chips were ever available?

You're missing the point.  Jeff isn't talking about OTS cost.
He's talking about fab costs as in how much it would cost
to fab X number of 386s to how much it would cost to fab
X number of F21s.  Since nobody makes 386s anymore
it would technically cost more to fab them today then it
would to buy quad 4 Pentiums but that's based on 
economy of scale rather than cost in silicon.  

>> It is a little like comparing C18 to Pentium.  Since
>> Pentium don't cost a couple of cents

> But where can I buy a C18 for a couple of cents? It's an unrealistic
> figure; even if they were packaged singly, and the C18 did cost a
> couple of cents to fabricate, the chip packaging alone would
> completely dominate the cost. 

That's part of the reason why multiple C18 cores are put on 
the same chip.

Regards,

John M. Drake


      

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