ATTiny85 and MIT core not running at 8Mhz?

joshuajnoble:
You're definitely right about the number of cycles per instruction, many thanks for reminding me about that! I've got the following code showing me 4 spikes per uS, hence 8Mhz if my math is right?

void loop()

{
 while(true) {
   PORTB |= 0x1; // set pin 1 so that it is at vcc
   PORTB &= 0xFE; // clear pin 1 so that it is grounded
 }
}

I'd say no...

"PORTB |= 0x1;" is a read of port B followed by an or and a write. That's going to be at least two clock cycles.

This is why my code used PINB - to avoid the read.