The function SYS_BASE returns the base address of the system variables.
POKE_W SYS_BASE+140,8 POKE_W SYS_BASE+142,3
Sets the key repeat delay.
Users peeking and poking in the System Variables should know what they are doing!
Minerva and SMS offer another technique to read and alter system variables but these are specific to Minerva and SMS whilst SYS_BASE works an every ROM. It is generally not advisable to access fixed addresses in memory as virtually everything can move around.