CODE (roll) ( "2 3 4 5 4 --> 2 4 5 5". See B311 )
    CX POPx, CX 2 ADDxi, CALL, lblchkPS @ RPCn, CX 2 SUBxi,
    SI SP MOVxx, SI CX ADDxx,
    DI SI MOVxx, DI 2 ADDxi, STD, REPZ, MOVSB,
;CODE
CODE 2DROP 2 chkPS, SP 4 ADDxi, ;CODE
CODE 2DUP 2 chkPS,
    AX POPx, BX POPx,
    BX PUSHx, AX PUSHx, BX PUSHx, AX PUSHx,
;CODE
CODE S0 AX PS_ADDR MOVxI, AX PUSHx, ;CODE
CODE 'S SP PUSHx, ;CODE
CODE AND 2 chkPS,
    AX POPx, BX POPx, AX BX ANDxx, AX PUSHx, ;CODE
CODE OR 2 chkPS,
    AX POPx, BX POPx, AX BX ORxx, AX PUSHx, ;CODE