diff --git a/cpu/avr/dev/clock-avr.h b/cpu/avr/dev/clock-avr.h
index 460e3d8c7..95bcfbc8e 100644
--- a/cpu/avr/dev/clock-avr.h
+++ b/cpu/avr/dev/clock-avr.h
@@ -14,11 +14,11 @@
 \
   /*						  \
    * Set comparison register: \
-   * Crystal freq. is 16000000,\
-   * pre-scale factor is 1024, i.e. we have 125 "ticks" / sec: \
-   * 16000000 = 1024 * 125 * 125 \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 1024, we want CLOCK_CONF_SECOND ticks / sec: \
+   * F_CPU = 1024 * CLOCK_CONF_SECOND * OCR0 \
    */ \
-  OCR0 = 125; \
+  OCR0 = F_CPU/1024UL/CLOCK_CONF_SECOND; \
 \
   /* 								\
    * Set timer control register: 	\
@@ -48,11 +48,11 @@
 \
   /*						  \
    * Set comparison register: \
-   * Crystal freq. is 8000000,\
-   * pre-scale factor is 1024, we want 125 ticks / sec: \
-   * 8000000 = 1024 * 126.01 * 62, less 1 for CTC mode \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 1024, we want CLOCK_CONF_SECOND ticks / sec: \
+   * F_CPU = 1024 * CLOCK_CONF_SECOND * OCR0A, less 1 for CTC mode \
    */ \
-  OCR0A = 61; \
+  OCR0A = F_CPU/1024/CLOCK_CONF_SECOND - 1; \
 \
   /* 								\
    * Set timer control register: 	\
@@ -92,10 +92,10 @@
   /*						  \
    * Set comparison register: \
    * Crystal freq. is 32768,\
-   * pre-scale factor is 8, we want 125 ticks / sec: \
-   * 32768 = 8 * 124.1 * 33, less 1 for CTC mode\
+   * pre-scale factor is 8, we want CLOCK_CONF_SECOND ticks / sec: \
+   * 32768 = 8 * CLOCK_CONF_SECOND * OCR2A, less 1 for CTC mode\
    */ \
-  OCR2A = 32; \
+  OCR2A = 32768/8/CLOCK_CONF_SECOND - 1; \
 \
   /* 								\
    * Set timer control register: 	\
@@ -124,11 +124,11 @@
 \
   /*						  \
    * Set comparison register: \
-   * Crystal freq. is 8000000,\
-   * pre-scale factor is 1024, we want 125 ticks / sec: \
-   * 8000000 = 1024 * 126.01 * 62, less 1 for CTC mode \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 1024, we want CLOCK_CONF_SECOND ticks / sec: \
+   * F_CPU = 1024 * CLOCK_CONF_SECOND * OCR2A, less 1 for CTC mode \
    */ \
-  OCR0A = 61; \
+  OCR0A = F_CPU/1024UL/CLOCK_CONF_SECOND - 1; \
 \
   /* 								\
    * Set timer control register: 	\
@@ -156,11 +156,10 @@
 \
   /*   \
    * Set comparison register: \
-   * Crystal freq. is 8000000,\
-   * pre-scale factor is 256, i.e. we have 125 "ticks" / sec: \
-   * 8000000 = 256 * 250 * 125 \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 256, want CLOCK_CONF_SECOND ticks / sec: \
    */ \
-  OCR0A = 250; \
+  OCR0A = F_CPU/256UL/CLOCK_CONF_SECOND - 1; \
 \
   /* \
    * Set timer control register: \
@@ -191,11 +190,11 @@
 \
   /*   \
    * Set comparison register: \
-   * Crystal freq. is 8000000,\
-   * pre-scale factor is 256, i.e. we have 125 "ticks" / sec: \
-   * 8000000 = 256 * 250 * 125 \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 256, we want CLOCK_CONF_SECOND ticks / sec: \
+   * F_CPU = 256 * CLOCK_CONF_SECOND * OCR0 \
    */ \
-  OCR0 = 250; \
+  OCR0 = F_CPU/256UL/CLOCK_CONF_SECOND; \
 \
   /* \
    * Set timer control register: \
@@ -223,11 +222,11 @@
 \
   /*   \
    * Set comparison register: \
-   * Crystal freq. is 8000000,\
-   * pre-scale factor is 256, i.e. we have 125 "ticks" / sec: \
-   * 8000000 = 256 * 250 * 125 \
+   * Crystal freq. is F_CPU,\
+   * pre-scale factor is 256, we want CLOCK_CONF_SECOND ticks / sec: \
+   * F_CPU = 256 * CLOCK_CONF_SECOND * OCR2 \
    */ \
-  OCR2 = 250; \
+  OCR2 = F_CPU/256UL/CLOCK_CONF_SECOND; \
 \
   /* \
    * Set timer control register: \
diff --git a/cpu/avr/rtimer-arch.c b/cpu/avr/rtimer-arch.c
index 08e39aa28..d5cec6d17 100644
--- a/cpu/avr/rtimer-arch.c
+++ b/cpu/avr/rtimer-arch.c
@@ -34,7 +34,8 @@
 /**
  * \file
  *         AVR-specific rtimer code
- *         Currently only works on ATMEGAs that have Timer 3.
+ *         Defaults to Timer3 for those ATMEGAs that have it.
+ *         If Timer3 not present Timer1 will be used.
  * \author
  *         Fredrik Osterlind <fros@sics.se>
  *         Joakim Eriksson <joakime@sics.se>
@@ -51,7 +52,6 @@
 #include "rtimer-arch.h"
 
 #if defined(__AVR_ATmega1281__) || defined(__AVR_ATmega1284P__)
-//#error FTH081029 test timer 3
 #define ETIMSK TIMSK3
 #define ETIFR TIFR3
 #define TICIE3 ICIE3
@@ -78,7 +78,7 @@
 #endif
 
 /*---------------------------------------------------------------------------*/
-#ifdef TCNT3
+#if defined(TCNT3) && RTIMER_ARCH_PRESCALER
 ISR (TIMER3_COMPA_vect) {
   ENERGEST_ON(ENERGEST_TYPE_IRQ);
 
@@ -104,6 +104,7 @@ ISR (TIMER1_COMPA_vect) {
 void
 rtimer_arch_init(void)
 {
+#if RTIMER_ARCH_PRESCALER
   /* Disable interrupts (store old state) */
   uint8_t sreg;
   sreg = SREG;
@@ -125,8 +126,19 @@ rtimer_arch_init(void)
   /* Reset counter */
   TCNT3 = 0;
 
-  /* Start clock, maximum prescaler (1024)*/
+#if RTIMER_ARCH_PRESCALER==1024
   TCCR3B |= 5;
+#elif RTIMER_ARCH_PRESCALER==256
+  TCCR3B |= 4;
+#elif RTIMER_ARCH_PRESCALER==64
+  TCCR3B |= 3;
+#elif RTIMER_ARCH_PRESCALER==8
+  TCCR3B |= 2;
+#elif RTIMER_ARCH_PRESCALER==1
+  TCCR3B |= 1;
+#else
+#error Timer3 PRESCALER factor not supported.
+#endif
 
 #elif RTIMER_ARCH_PRESCALER
   /* Leave timer1 alone if PRESCALER set to zero */
@@ -154,18 +166,20 @@ rtimer_arch_init(void)
 #elif RTIMER_ARCH_PRESCALER==1
   TCCR1B |= 1;
 #else
-#error PRESCALER factor not supported.
+#error Timer1 PRESCALER factor not supported.
 #endif
 
 #endif /* TCNT3 */
 
   /* Restore interrupt state */
   SREG = sreg;
+#endif /* RTIMER_ARCH_PRESCALER */
 }
 /*---------------------------------------------------------------------------*/
 void
 rtimer_arch_schedule(rtimer_clock_t t)
 {
+#if RTIMER_ARCH_PRESCALER
   /* Disable interrupts (store old state) */
   uint8_t sreg;
   sreg = SREG;
@@ -190,4 +204,5 @@ rtimer_arch_schedule(rtimer_clock_t t)
 
   /* Restore interrupt state */
   SREG = sreg;
+#endif /* RTIMER_ARCH_PRESCALER */
 }
diff --git a/cpu/avr/rtimer-arch.h b/cpu/avr/rtimer-arch.h
index dae4b0968..533ea0507 100644
--- a/cpu/avr/rtimer-arch.h
+++ b/cpu/avr/rtimer-arch.h
@@ -36,16 +36,22 @@
 
 #include <avr/interrupt.h>
 
-/* Nominal ARCH_SECOND is F_CPU/prescaler, e.g. 8000000/1024 = 7812 */
+/* Nominal ARCH_SECOND is F_CPU/prescaler, e.g. 8000000/1024 = 7812
+ * Other prescaler values (1, 8, 64, 256) will give greater precision
+ * with shorter maximum intervals.
+ * Setting RTIMER_ARCH_PRESCALER to 0 will leave Timers alone.
+ * rtimer_arch_now() will then return 0, likely hanging the cpu if used.
+ * Timer1 is used if Timer3 is not available.
+ */
 #ifndef RTIMER_ARCH_PRESCALER
 #define RTIMER_ARCH_PRESCALER 1024UL
 #endif
+#if RTIMER_ARCH_PRESCALER
 #define RTIMER_ARCH_SECOND (F_CPU/RTIMER_ARCH_PRESCALER)
+#else
+#define RTIMER_ARCH_SECOND 0
+#endif
 
-/* Use TCNT1 if TCNT3 not available.
- * Setting RTIMER_ARCH_PRESCALER to 0 will leave timer1 alone.
- * Obviously this will disable rtimers.
- */
 
 #ifdef TCNT3
 #define rtimer_arch_now() (TCNT3)
diff --git a/platform/avr-raven/apps/raven-lcd-interface/raven-lcd.c b/platform/avr-raven/apps/raven-lcd-interface/raven-lcd.c
index 95e4bc8de..dafc52a9b 100644
--- a/platform/avr-raven/apps/raven-lcd-interface/raven-lcd.c
+++ b/platform/avr-raven/apps/raven-lcd-interface/raven-lcd.c
@@ -28,7 +28,6 @@
  *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  *  POSSIBILITY OF SUCH DAMAGE.
  *
- * $Id: raven-lcd.c,v 1.11 2010/12/22 17:09:03 dak664 Exp $
 */
 
 /**
@@ -166,7 +165,7 @@ char serial_char_received;
 /*---------------------------------------------------------------------------*/
 /* Sleep for howlong seconds, or until UART interrupt if howlong==0.
  * Uses TIMER2 with external 32768 Hz crystal to sleep in 1 second multiples.
- * TIMER2 may have already been set up for 125 ticks/second in clock.c
+ * TIMER2 may have already been set up for CLOCK_CONF_SECOND ticks/second in clock.c
 
  *
  * Until someone figures out how to get UART to wake from powerdown,
diff --git a/platform/avr-raven/contiki-conf.h b/platform/avr-raven/contiki-conf.h
index fa7921879..9f4983413 100644
--- a/platform/avr-raven/contiki-conf.h
+++ b/platform/avr-raven/contiki-conf.h
@@ -68,15 +68,21 @@ unsigned long clock_seconds(void);
 #define INFINITE_TIME 0xffff
 
 /* Clock ticks per second */
-#define CLOCK_CONF_SECOND 125
+#define CLOCK_CONF_SECOND 128
 
-/* Maximum tick interval is 0xffff/125 = 524 seconds */
-#define RIME_CONF_BROADCAST_ANNOUNCEMENT_MAX_TIME CLOCK_CONF_SECOND * 524UL /* Default uses 600UL */
-#define COLLECT_CONF_BROADCAST_ANNOUNCEMENT_MAX_TIME CLOCK_CONF_SECOND * 524UL /* Default uses 600UL */
+/* Maximum tick interval is 0xffff/128 = 511 seconds */
+#define RIME_CONF_BROADCAST_ANNOUNCEMENT_MAX_TIME INFINITE_TIME/CLOCK_CONF_SECOND /* Default uses 600 */
+#define COLLECT_CONF_BROADCAST_ANNOUNCEMENT_MAX_TIME INFINITE_TIME/CLOCK_CONF_SECOND /* Default uses 600 */
 
 /* The 1284p can use TIMER2 with the external 32768Hz crystal to keep time. Else TIMER0 is used. */
 /* The sleep timer in raven-lcd.c also uses the crystal and adds a TIMER2 interrupt routine if not already define by clock.c */
-#define AVR_CONF_USE32KCRYSTAL 0
+#define AVR_CONF_USE32KCRYSTAL 1
+
+/* Rtimer is implemented through the 16 bit Timer1, clocked at F_CPU through a 1024 prescaler. */
+/* This gives 7812 counts per second, 128 microsecond precision and maximum interval 8.388 seconds. */
+/* Change clock source and prescaler for greater precision and shorter maximum interval. */
+/* 0 will disable the Rtimer code */
+//#define RTIMER_ARCH_PRESCALER 256UL /*0, 1, 8, 64, 256, 1024 */
 
 /* COM port to be used for SLIP connection. Not tested on Raven */
 #define SLIP_PORT RS232_PORT_0
@@ -103,7 +109,7 @@ unsigned long clock_seconds(void);
 #define UIP_CONF_ICMP6            1
 #define UIP_CONF_UDP              1
 #define UIP_CONF_TCP              1
-#define UIP_CONF_IPV6_RPL         1
+#define UIP_CONF_IPV6_RPL         0
 #define NETSTACK_CONF_NETWORK       sicslowpan_driver
 #define SICSLOWPAN_CONF_COMPRESSION SICSLOWPAN_COMPRESSION_HC06
 #else
diff --git a/platform/avr-raven/contiki-raven-main.c b/platform/avr-raven/contiki-raven-main.c
index 71220e43d..1758274ce 100644
--- a/platform/avr-raven/contiki-raven-main.c
+++ b/platform/avr-raven/contiki-raven-main.c
@@ -97,9 +97,9 @@
 #define TESTRTIMER 0
 #if TESTRTIMER
 //#define PINGS 64
-#define ROUTES 64
-#define STAMPS 30
-#define STACKMONITOR 128
+#define ROUTES 300
+#define STAMPS 60
+#define STACKMONITOR 600
 
 uint8_t rtimerflag=1;
 uint16_t rtime;
@@ -416,10 +416,9 @@ main(void)
 #endif
 
 #if TESTRTIMER
-/* Timeout can be increased up to 8 seconds maximum.
+/* Timeout can be increased up to 8 seconds maximum (at 8MHz with 1024 prescaler)
  * A one second cycle is convenient for triggering the various debug printouts.
  * The triggers are staggered to avoid printing everything at once.
- * My raven is 6% slow.
  */
     if (rtimerflag) {
       rtimer_set(&rt, RTIMER_NOW()+ RTIMER_ARCH_SECOND*1UL, 1,(void *) rtimercycle, NULL);