Wrong simulation time for Dallas DS89C420 ?

Hi, here is code:

void float_test( void )
{
int a;
float f;

f=4.44;
for(a=0; a<100; a++)
f *= f/2.25;
}

I use simulator for simulating execution time of shown function.
When I select device AT89c51, execution time is about 100ms ( Xtal = 12MHz ).
When DS89C420 is selected, execution time is about 45ms ( with saame Ctal = 12MHz )

From datasheet's: AT89c51 run on Xtal/12, DS89C420 runs on Xtal, so:

is there a explanation why simulated execution time on Dallas chip is only 2x faster?

Thanks,
Boris