Overclocking

Wiki
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As explained in the Pokitto Magazine volume 1, page 34, it is safe to set your Pokitto’s clockspeed to 72mhz by setting _OSCT=2. This can’t be done by making a #define in your code.

Here are instructions depending on which IDE you’re using (this is a wiki, feel free to add more):

  • PyInSky:
    Python games run at 72mhz by default.

  • FemtoIDE (C++):
    Open project.json and add "-D_OSCT=2" to the Pokitto section in CPPFlags and CFlags.

  • FemtoIDE (Java):
    Open project.json and add "-D_OSCT=2" to the Pokitto section in CPPFlags and add "--defsym=_OSCT=2" to the Pokitto section in SFlags.

  • Makefile:

C_FLAGS += '-D_OSCT=2'
CXX_FLAGS += '-D_OSCT=2'

  • Embitz:
    In project properties - build settings - defines tab, add _OSCT=2

  • PlatformIO:
    -D _OSCT=2 in build_flags in platformio.ini, e.g.

build_flags =
  -D _OSCT=2
  -std=c++11

Extra notes:

  • Overclocking has no effect on the Simulator.
  • The Emulator will increase the amount of instructions that it needs to execute per second, but if your computer can’t handle the extra work, overclocking will actually result in a slowdown.
4 Likes
2

It can’t? It seems to be working for me (putting in My_settings.h). FPS is going way up.

3

The FPS number goes up, but is it actually getting any faster?
The code that actually changes the speed is in mbed’s system file, which does not include My_settings.h.

4

Not sure, I trusted the FPS :smiley: I’ll take a closer look at it.

5

If in the #defines, the clock counter will speed up and the fps will appear faster. But for OSCT to actually affect the SysClock speed, it has to be given on the build settings

6

I have a stupid question… would overclocking mess up the RTC time ?

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7

Not a stupid question at all

The RTC has its own 32kHz crystal exactly for these kind of reasons. It is independent of the core

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8

Maybe another stupid question: are there negative side effects by doing this overclocking? Or are there situations where you definitely would not want to use overclocking?

9

sd card reading fails sometimes

sometimes there is a little noise on screen

10

Ah the price of going ludicrous speed.

11

Doesn’t it have an impact on the produced heat and consequently also on the lifespan of the pokitto?
Or is this effect very limited?

12

The same core runs at 100Mhz in the LPC M4F dual-core (M4 & M0) chip.

72 Mhz is nothing for modern chips

13

Ok nothing to worry about then :smile:

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14

I don’t fully understand how to do this in Embitz.
Where do you add this _OSCT=2?

15

In project properties - build settings - defines tab

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16

If I go to project properties, there is no such thing as build settings

image
image726×974 20.7 KB

However there is a Project build options:

image
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And here I do not find the defines tab…

Maybe I should be looking somewhere else?

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17

I do see a #defines tab on that screenshot…

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18

Derp
Derp834×554 16.7 KB

If I get chance I’ll look into improving the instructions and/or maybe finding a better way than doing it per-project, but I don’t really use EmBitz much anymore (partly because I got fed up with dealing with those build settings menus).

19

Ok I have found it now… I was a bit confused by the # symbol, thinking that would result in a regular #define

20

Technically it is a regular define,
but it has to be defined before the compiler even starts for the right library to see it and respond to it.

(Or that’s how I understood it anway.)

Putting it in the #define tab basically makes the IDE pass the right command line option to the compiler to make sure it’s defined at the start of compilation.