lblchkPS BSET ( CX -> expected size )
AX PS_ADDR MOVxI, AX SP SUBxx, 2 SUBAXI, ( CALL adjust )
AX CX CMPxx,
IFNC, ( we're good ) RETn, THEN,
( underflow ) DI 0x06 MOVxm, JMPs, lblexec @ RPCs,