// execute a loop in slow memory and also in fast memory.
// time both loop executions and store the result in $2000-$2003

// showed that stray writes also happened to the VIA timer registers

 
VIA	=$e840
T2L	=VIA + 8
T2H	=VIA + 9
ACR	=VIA + 11

; define for including fast code check, undefine for slow only
; address of code in fast memory
FAST	=$081100

	*=$1000

	sei
	
	; native mode
	clc
	xce

	lda ACR
	and #%11011111
	sta ACR
	
	jmp @start	; jmp long, so it can be patched to mirror RAM at @$30xxxx
start	
	lda #0
	sta T2L
	sta T2H

	; delay loop to check
	ldx #0
l1 	dex
	bne l1
	lda T2L
	ldx T2H
end
	sta $2000
	stx $2001

	jmp @end2	; jmp long from mirror RAM to bank 0
end2

#ifldef FAST

len = end - start
	
	; copy over the loop from "start" to "end" to fast RAM
	ldx #len-1
l2	lda start,x
	sta @FAST,x
	dex
	bpl l2

	; add long jump back to this slow code
	lda #$5c
	sta @FAST+len
	lda #<done
	sta @FAST+len+1
	lda #>done
	sta @FAST+len+2
	lda #0
	sta @FAST+len+3

	; execute fast loop
	jmp @FAST

	; returns here
done
	sta $2002
	stx $2003
#endif

	; emulation mode
	.xs
	sec
	xce
	cli
	brk