; same init stuff the kernel calls after reset
        ldx #0
        stx $d016
        jsr $ff84   ; Initialise I/O

        jsr init_system_constants_light ; faster replacement for $ff87
        jsr $ff8a   ; Restore Kernal Vectors
        jsr $ff81   ; Initialize screen editor


...

; ------------------------------------------------------------------------
; faster replacement for $ff87
init_system_constants_light:
        ; from KERNAL @ FD50:
        lda #$00
        tay
:
        sta $0002,y
        sta $0200,y
        sta $0300,y
        iny
        bne :-
        ldx #$3c
        ldy #$03
        stx $b2
        sty $b3
        tay

        ; result from loop KERNAL @ FD6C:
        lda #$00
        sta $c1
        sta $0283
        lda #$a0
        sta $c2
        sta $0284

        ; from KERNAL @ FD90:
        lda #$08
        sta $0282       ; pointer: bottom of memory for operating system
        lda #$04
        sta $0288       ; high byte of screen memory address
        rts