Why does the PIC slow down when I connect some current loads?

[Tricka90]

I'm making a PIC controlled LED lamp. I'm noticing that every LED I add to the circuit the PIC program slows down more. Why is it happening and how can I work around this problem?
I'm using a PIC 16F876 with 12MHz chrystal oscillator.
If you need more information I'll be happy to give them.

[ve7xen]

Are you changing the code when you add an LED? If the PIC is clocked from a crystal it won't appreciably change speed just because you've changed the load on its IO pins. Something in your code has changed, or is behaving differently, when you're adding the LEDs.

Posting your code may help.

[dannyf]

I'm noticing that every LED I add to the circuit the PIC program slows down more.

You must be living in an alternate universe, .

Seriously, what exactly did you observe that led you to  that conclusion?

[Psi]

My guess is he's doing some sort of matrix or pwm

[Jeroen3]

If you are running from internal oscillator, or any other external crystal which requires schmitt triggering, and the LED's are directly on the pic pins you might be exceeding maximum current limits.
Causing voltage drop, causing oscillator artifacts.

[WarSim]

If you are running from internal oscillator, or any other external crystal which requires schmitt triggering, and the LED's are directly on the pic pins you might be exceeding maximum current limits.
Causing voltage drop, causing oscillator artifacts.

I agree with your assessment.  All PIC FRCs have voltage for speed requirements.  You may be browning out the chip slowing the FRC OSC or even triggering the BOR whenever you turn on too many LEDs.  Either way it is starving for attention (pun).  :-)

[dannyf]

My guess is he's doing some sort of matrix or pwm

Yes, likely polling.