[SOLVED ]NEED HELP with ATtiny13-20PU

I have programmed my Attiny with an Arduino UNO with ''Arduino as ISP''.
The program is just Blink to pin 4 on my Attiny.
Problem lies here:

When i have connected just pin 8 to Uno 5v, and pin 4 to Uno GND, everything works perfectly fine and my LED blinks every second.

BUT, when i connect pin 8 to power supply + and pin 4 to power supply -, all hell breaks loose.
Diode does a blink or two just fine, but then the timing is messed up and blinks rapidly. The power supply is set to 5V.

My settings

Any idea what may cause the problem?

Do you have a decoupling cap connected between pin 8 and pin 4?

No, i didn't have it there, thanks. Solved.

Excellent! Thanks for letting us know the issue is solved and I’m glad you got it working :slight_smile: