diff --git a/main.S b/main.S
index e6b5978..cf5a9a0 100644
--- a/main.S
+++ b/main.S
@@ -39,20 +39,30 @@ main_asm:
 .global int_horizontal_sync_s
 int_horizontal_sync_s:
     push r31
+    push r30
 
     ; load timer to trigger isr at the beginning of the visible scanline
+    ; reset counter to 0
     ldi r31, 0
-    sts TCNT0, r31
-    lds r31, hpos       ; set counter TOP
-    sts OCR0A, r31
+    sts TCNT1H, r31
+    sts TCNT1L, r31
 
-    ldi r31, 0x7        ; clear any pending interrupt
-    sts TIFR0, r31
+    ; set counter TOP (MSB first!)
+    lds r31, hpos + 1
+    lds r30, hpos
+    sts OCR1AH, r31
+    sts OCR1AL, r30
 
-    lds r31, TIMSK0
-    ori r31, 0x02       ; mask enable interrupt timer A
-    sts TIMSK0, r31
+    ; clear any pending interrupt
+    ldi r31, 0x7
+    sts TIFR1, r31
 
+    ; enable interrupt timer A
+    lds r31, TIMSK1
+    ori r31, 0x02
+    sts TIMSK1, r31
+
+    pop r30
     pop r31
     ret
 
@@ -67,9 +77,9 @@ int_timer_0:
     push r25
 
     ; turn off interrupt
-    lds r31, TIMSK0
+    lds r31, TIMSK1
     andi r31, 0xfd      ; mask disable interrupt timer A
-    sts TIMSK0, r31
+    sts TIMSK1, r31
 
     lds r31, show_image
     cpi r31, 0x1
diff --git a/main.c b/main.c
index a07a29e..f430d8c 100644
--- a/main.c
+++ b/main.c
@@ -20,7 +20,7 @@ volatile uint8_t image = 0xff;
 
 // horizontal and vertical position of bouncing logo
 volatile uint8_t vpos = 0;
-volatile uint8_t hpos = 0;
+volatile uint16_t hpos = 0;
 volatile int8_t vinc = +1;
 volatile int8_t hinc = +1;
 
@@ -36,7 +36,7 @@ ISR(INT0_vect) {
     vinc = -1;
   if (hpos == HORIZONTAL_OFFSET)
     hinc = +1;
-  if (hpos == 255 - 40)
+  if (hpos == 1024 - 80)
     hinc = -1;
 
   int_vertical_sync_s();
@@ -53,7 +53,7 @@ ISR(INT1_vect) {
     int_horizontal_sync_s();
 }
 
-ISR(TIMER0_COMPA_vect, ISR_NAKED) {
+ISR(TIMER1_COMPA_vect, ISR_NAKED) {
   // back porch timer interrupt
   asm("jmp int_timer_0");
 }
@@ -73,9 +73,13 @@ int main() {
   EICRA = 0x0a; // external interrupt 0 and 1, falling edge
   EIMSK = 0x03; // external interrupt 0 and 1, mask enable
 
-  TCCR0A = 0x02; // don't connect output pins to timer, CTC[1:0] mode
+  TCCR1A = 0x00; // don't connect output pins to timer, CTC[1:0] mode
+  TCCR1B = 0x09; // CTC[3:2] mode, no prescaler
 
+#if 0
+  TCCR0A = 0x02; // don't connect output pins to timer, CTC[1:0] mode
   TCCR0B = 0x01; // CTC[2] mode, no prescaler
+#endif
 
   main_asm();
 }