How do I set the correct f_cpu speed in boards.txt with no side effects?

Other Hardware 3rd Party Boards
1

Hi guys, I'm using an arduino UNO for programing the attiny85 20PU and I'm facing some issues with the boards.txt file. I'm using this definition

attiny85arduinoisp.name=ATtiny85 (w/ Arduino as ISP)
attiny85arduinoisp.upload.using=arduino:arduinoisp
attiny85arduinoisp.upload.maximum_size=8192
attiny85arduinoisp.build.mcu=attiny85
attiny85arduinoisp.build.f_cpu=1000000L
attiny85arduinoisp.build.core=attiny45_85

but from my understanding f_cpu value is incorrect and it needs to be changed to 200000L for 20MHz chips, but when I do that and I load a simple blinking light sketch to the attiny85 the timing is totally off, delay(1000) lasts more than 1sec...
Any ideas what am I doing wrong?
Thanks!

2

manorius:
but from my understanding f_cpu value is incorrect and it needs to be changed to 200000L for 20MHz chips
Any ideas what am I doing wrong?

Two orders of magnitude.

3

So double clock speed double time?
And how do I bring it back to normal, so that 1000 is one sec?

4

manorius:
So double clock speed double time?

No. Your value for F_CPU is very wrong.

5

manorius:
So double clock speed double time?

Look up "order of magnitude" in a dictionary.

6

fungus:

manorius:
So double clock speed double time?

Look up "order of magnitude" in a dictionary.

To be fair, an order of magnitude in binary is 2 ;).

7

The build.f_cpu values are in Hz, so ie. in order to setup it to 20MHz:
.. = 20000000L

8

Note that you set up the CPU clock to 200KHz! Not 20MHz.