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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.forth
Subject: Re: OT (slightly) What is the "best" processor for a new project?
Date: Wed, 29 May 2013 11:05:33 -0700
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rickman <gnuarm@gmail.com> writes:
> WOW!  0 for 3!!!  A MISC processor in an FPGA can easily run at over
> 50 MHz.

How does 50 mhz of misc performance compare to 50 mhz of Cortex M0+
perforamnce?  What about compared to 200 mhz of Cortex M4F performance?

> I believe the J1 runs at around 100 MHz ...  So obviously there is
> no performance hit relative to most MCUs.

I'd like to know how it compared to MCU's with similar power consumption
to the FPGA.  In most situations, I'd also ask about comparable cost,
but Howerd has said in this instance, cost doesn't matter much.

> I can get an FPGA for $3 which will host a MISC CPU and have plenty of
> room left for other logic like custom interfaces that you can't do
> with a standard MCU. 

Right, I understand that, and it's why I said "or unless you already
need the FPGA for some other reason, and want to put a minimal cpu onto
part of it".  It's one of the actual valid use cases.  And I don't think
a MISC on a $3 FPGA can compare to a $3 Cortex part as a computing
device.  For one thing, Howerd wanted 128k of program memory.  Where are
you going to put that on your $3 FPGA?  Does the $3 FPGA have any block
ram?  Any DSP slices?

> There are FPGAs which rival MCUs in terms of power consumption
> reaching double digit uAs quiescent power and low mAs at MHz clock
> rates.  Check out the iCE40 product line from Lattice.

I don't understand this stuff enough to make performance estimates from
those data sheets.  Given Howerd's specs, we're reaching towards
upper-midrange MCU territory though below application processors.  So
I'd be interested to know how softcore power consumption compares with
midrange MCU's, running the actual sorts of programs run on those sorts
of MCU's.  Also with the lowest powered MCU's.