DEFINE OSC too limited

[breogan]

Hi,
I'm trying to use 20MHz oscillator with PIC16C74A, for example, I have written this program to make blink a led for 1 second, but it doesn't work, the frequency is not 1Hz (it is more slow):

'********** Definitions **********
DEFINE OSC 20

'********** Main prog **********
Main:
high PORTA.0
pause 500
low PORTA.0
pause 500
goto Main

End

'***************************************

I'm using the David Tait programmer (home made) with the PIC74.EXE program (PIC16C74 Programmer Version 1.0b Copyright (C) 1996 Paul Vollebregt.) With the options "-hp8" (HS osc), also I have triyed with "-xp8" (XT osc).

Thanks !