Microchip PIC32MZ Flash Microcontroller is the World's Fastest 32-bit MCU

In comp.arch.embedded,
Tim Wescott <tim@seemywebsite.really> wrote:
> On Fri, 22 Nov 2013 11:20:36 +0100, Stef wrote:
>> 
>> Where you looking for cpu's with dual-precision FP? Did you find any
>> smallish ones? I'm looking for such a processor myself and it seems only
>> the bigger CPU's have DP FP. Seems to start with Cortex A5 and this
>> e300.
>> Processors like M4 and SHARC only have single precision FPU's.
>
> The MPC5200 seems to be the most embeddable one that I've found.
>
> DP floating point hardware is just big; that probably drives the "only 
> big processors have DP floating point" issue.

So far I have similar findings, thanks for the confirmation.

> What are you doing?  You may be able to solve your problem with fixed-
> point arithmetic and cleverness -- in my recent search, had I not talked 
> my way into a spot on a big processor I would have seriously considered 
> 64-bit fixed point, and there's a huge class of control system problems 
> that just can't be done with 32-bit floating point that work great with 
> 32-bit fixed point.

This is a measurement that requires (amongst other things) a non-linear
fitting procedure with the Levenberg&ndash;Marquardt algorithm on a few thousand
samples. We already found that disabling denormals does not significantly
affect the results (but it is noticeable) and gives a huge speed increase.

Going back to 32-bit floating point or 64/32-bit fixed point will require
testing on a lot of data and of course modifying the code (there are
also some math lib functions involved in the calculation). This is not off
the option list, but needs to be compared with 'safe' solutions (sticking
with double precision floating point).

-- 
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

He:	Let's end it all, bequeathin' our brains to science.
She:	What?!?  Science got enough trouble with their OWN brains.
		-- Walt Kelly

In comp.arch.embedded,
Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> wrote:
> In comp.arch.embedded,
> Tim Wescott <tim@seemywebsite.really> wrote:
>> On Fri, 22 Nov 2013 11:20:36 +0100, Stef wrote:
>>> 
>>> Where you looking for cpu's with dual-precision FP? Did you find any
>>> smallish ones? I'm looking for such a processor myself and it seems only
>>> the bigger CPU's have DP FP. Seems to start with Cortex A5 and this
>>> e300.
>>> Processors like M4 and SHARC only have single precision FPU's.
>>
>> The MPC5200 seems to be the most embeddable one that I've found.
>>
>> DP floating point hardware is just big; that probably drives the "only 
>> big processors have DP floating point" issue.
>
> So far I have similar findings, thanks for the confirmation.

Just had a better look at the Cortex-Rx, I somehow skipped over this one
earlier. The R4 always has a double precision FPU, the R5 and R7 have an
option for double precision or optimized single precision.

TI has for instance the Hercules safety controllers with R4 core,
starting at LQFP-144 packages. Interesting, not sure it can handle the
memory requirements for our application (which are still under
investigation btw).

The safety aspect of these controlers may be a plus for the intended
application.

-- 
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

There comes a time in the affairs of a man when he has to take the bull
by the tail and face the situation.
		-- W.C. Fields