Embedded board with good support out of the box?

Steve B sbattazzo at gmail.com
Fri May 22 20:22:18 UTC 2015

On Fri, May 22, 2015 at 9:48 AM, Karel Gardas <karel.gardas at centrum.cz>

> On 05/22/15 06:28 PM, Mr. Andrei Chichak wrote:
>> On 2015-May-22, at 8:58 AM, Steve B <sbattazzo at gmail.com> wrote:
>>  The STM32F4 is on my list, but because our main number-crunching routine
>>> already takes 25% of our time step duty cycle on the AM3358 at 1GHz, it
>>> seems risky. If we pretend MIPS/MHz and FLOPS/MHz were a 1:1 map from the
>>> A8 to the M4, then we are guaranteed to violate timing. On the flip side,
>>> this number crunching part is not in any way optimized with embedded
>>> operation in mind, so there are at least a couple things I can think of  we
>>> could do that may allow us to squeeze it in to a Cortex M device.
>> I think 1:1 would be optimistic, but you also don’t have to deal with a
>> heavy OS or things like demand paged virtual memory.
> AM3358 is Cortex-A8 IIRC which means in-order dual-issue CPU. On the other
> hand IIRC M4 is single issue in-order CPU so it's definitely not 1:1. Also
> wikipedia lists M4 as 1.25 DMIPS/MHz and A8 as 2.0 DMIPS/MHz. To get to A8
> performance level, you would need brand new M7 which provides 2.14
> DMIPS/MHz[1].
> Karel
> [1]: http://en.wikipedia.org/wiki/List_of_ARM_microarchitectures
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Thanks, good call! The M7 was also on my mind (supposed to be better
floating point performance than the M4 as well?), but it's still only in
engineering sample stage I think. The only vendor I know of that has a
board out for it is Emcraft systems, but it's not yet using "production"

The STM32F7 is supposed to be binary compatible with the F4 so hopefully it
wouldn't be too hard to get RTEMS going on that.

For now I think it's simplest to just try to trim the fat (double->single,
etc) and run on the same platform we currently have, and see how big of an
execution time gain can be had from just that, and then I'll have a better
idea of whether or not the M4 or M7 is feasible.
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