Is it possible to bypass clock frequency limit of CCS ?

[WalkOver]

Hello,

I know this is not recommended, but I would like to try to overclock a dsPIC33EP.
This is not possible with CCS. You can't exceed the official maximum clock speed.
Is there a way to remove this limitation ?

Thank you very much

[Ttelmah]

On most of the DSPIC's, you can change the clock rate by manually setting
the PLLFBD register. However unlike a lot of the older chips, the clock rates
have very little margin. The clocks have comments like:
"This frequency range must be met at all times", and in fact the chips are
often borderline for cooling, even 'at' their rated frequencies.
However the compiler usually does not limit this. It may well be refusing
because there is no PLL option to get to the frequency.
For example on my current chip it won't allow you to select 150MHz, but does
if you use an external oscillator at a slightly higher frequency than the internal
RC. On the RC there is not a PLL ratio that gives a frequency much above the
rated max.

[WalkOver]

Hello Ttelmah,

I think there is a limitation on CCS because when using this directive:

[Ttelmah]

Have a boot clock=, and then a second #use delay after you change
the PLL.
What chip?

[newguy]

As Ttelmah has stated, you can "manually" do anything you want via register-level access to the clock. The dsPICs have a 7.37MHz internal oscillator - boot from that, then attempt a switchover to something out of spec. After that, flash an LED or toggle a line (observe with a scope) just to see if the change worked and if the processor is actually running at the new speed.

http://www.ccsinfo.com/forum/viewtopic.php?p=159723&highlight=crystal#159723

[Ttelmah]

Also remember that when you overclock, other things can often go wrong. So
(for instance) the SPI, UART or ADC are ones that will often fail. The failures
are commonly intermittent and only when temperatures rise. I consider
most of the DsPIC's 'too close to their limit', to be reliably overclocked. I
usually underclock them since I have had several develop oddities at their
rated clock rates when temperatures get high...