A question about XC167CI simulator speed

Hello all,
I have used dave to setup a CPU speed to 20Mhz, by

PLLCON         =  0x7814;      // load PLL control register

To my surprise, while simulating a XC167CI, an interrupt that was programmed to occur every 5[ms] actually occured every 1[ms]. setting the CLKCFG did not have any effect (while simulating a XC167CR was influeced by the XTAL setting). is there another element that I should have setup besides PLLCON?