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

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!

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.

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

manorius:
So double clock speed double time?

No. Your value for F_CPU is very wrong.

manorius: So double clock speed double time?

Look up "order of magnitude" in a dictionary.

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 ;).

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

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