+@present:
+ ldx #VDC_CSET ; determine size of RAM...
+ jsr vdcgetreg
+ sta tmp1
+ ora #%00010000
+ jsr vdcputreg ; turn on 64k
+
+ jsr settestadr1 ; save original value of test byte
+ jsr vdcgetbyte
+ sta tmp2
+
+ lda #$55 ; write $55 here
+ ldy #ptr1
+ jsr test64k ; read it here and there
+ lda #$aa ; write $aa here
+ ldy #ptr2
+ jsr test64k ; read it here and there
+
+ jsr settestadr1
+ lda tmp2
+ jsr vdcputbyte ; restore original value of test byte
+
+ lda ptr1 ; do bytes match?
+ cmp ptr1+1
+ bne @have64k
+ lda ptr2
+ cmp ptr2+1
+ bne @have64k