Application with SoftDevice is faster by 20% as without it

[Despair1337]

Hello,

This issue is related to this ticket, before continuing I recommend to read it first.

I had suspicion that the "speed" improvement is between project compiled by SEGGER and GCC,
but the differences was veeery huge, and I couldn't believe that it's just thanks to better runtime library.

After comparing those two projects, I figured out that project which is using GCC doesn't use Softdevice, where SEGGER one uses it.

So I made GCC project with Softdevice, and well, results are pretty interesting:

GCC Newlib (No Softdevice): 1754609 cycles
GCC Newlib (SoftDevice): 1390996 cycles

(Less the better)

So there is performance upgrade by 20% when SoftDevice is used.

The benchmark code is 100%, and even when comparing both project makefiles, no compiler configuration differences are there, only
difference is that Softdevice is added.

Thus my question is, what Softdevice does that there is such huge performance improvement?

Thanks,
with regards,
Marek Kraus

[Vidar Berg]

Hi Marek,

It must be because the Softdevice enables the instruction cache by default: Cache.

You can add this line on startup to enable instruction cache in your non-softdevice project:

NRF_NVMC->ICACHECNF= NVMC_ICACHECNF_CACHEEN_Enabled;

Best regards,

Vidar

[Despair1337]

Hi Vidar,

Thank you very much, I tested it and it works perfectly,

Thank you for your time,
with regards,
Marek Kraus