diff --git a/Makefile b/Makefile
index 8559ad6..056d7a2 100644
--- a/Makefile
+++ b/Makefile
@@ -28,7 +28,7 @@ clean:
 	rm -rf $(cobj) $(gasmobj) $(deps) *.bin *.elf *.map
 
 run: $(KERNEL)
-	qemu-system-aarch64 -machine raspi3b -kernel $<
+	qemu-system-aarch64 -machine raspi3b -kernel $< -serial stdio
 
 debug: CFLAGS += $(DEBUG_FLAGS)
 debug: CXXFLAGS += $(DEBUG_FLAGS)
diff --git a/hello.c b/hello.c
index 75514e4..886bc59 100644
--- a/hello.c
+++ b/hello.c
@@ -1,7 +1,28 @@
 #include "uart.h"
+#include "mbox.h"
 
 int kernelmain(void) {
   init_uart();
+  mbox[0] = 8 * 4;
+  mbox[1] = MBOX_REQUEST;
+  mbox[2] = MBOX_TAG_GETVCOREMEM;
+  mbox[3] = 8;
+  mbox[4] = 0;
+  mbox[5] = 0;
+  mbox[6] = 0;
+  mbox[7] = MBOX_TAG_LAST;
+
+  if(mbox_call(MBOX_CH_PROP, mbox)){
+    puts("videocore start at 0x");
+    printhex(mbox[5]);
+    puts(" - ");
+    int mem = mbox[6]/1024/1024;
+    printdec(mem);
+    puts(" Mo\n");
+  }else{
+    puts("Error getting videocore mem\n");
+  }
+
   puts("Hello world\n");
   return 0;
 }
diff --git a/mbox.c b/mbox.c
new file mode 100644
index 0000000..a80955c
--- /dev/null
+++ b/mbox.c
@@ -0,0 +1,43 @@
+#include "mbox.h"
+
+// See at https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
+// For messsage description
+// E.g. for Get firmware revision
+//
+//    Tag: 0x00000001
+//    Request:
+//        Length: 0
+//    Response:
+//        Length: 4
+//        Value:
+//            u32: firmware revision
+//  mbox[0] = 4 * 6 // total length in byte
+//  mbox[1] = MBOX_REQUEST
+//  mbox[2] = 0x00000001
+//  mbox[3] = max(req_length, resp_length) -> 4
+//  mbox[5] = 0 // 0 :request, 0x80000000: response
+//  mbox[6] = MBOX_TAG_LAST
+
+
+// aligned on 16 mutiple so the 4 first bit can be used by the channel
+// Should be allocated in the first 2^32bytes
+volatile uint32_t __attribute__((aligned(16))) mbox[36];
+
+int mbox_call(uint8_t ch, volatile uint32_t *box) {
+  // mbox is 16 aligned
+  uint32_t r = (uint64_t)box | (ch & 0xF);
+  while (*MBOX_STATUS & MBOX_FULL) {
+    asm volatile("nop");
+  }
+  *MBOX_WRITE = r;
+  while (1) {
+    while (*MBOX_STATUS & MBOX_EMPTY) {
+      asm volatile("nop");
+    }
+    if (r == *MBOX_READ)
+      /* is it a valid successful response? */
+      return box[1] == MBOX_RESPONSE;
+  }
+
+  return 0;
+}
diff --git a/mbox.h b/mbox.h
new file mode 100644
index 0000000..4ca0017
--- /dev/null
+++ b/mbox.h
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <stdint.h>
+#include "mmio.h"
+
+#define MBOX_READ       ((volatile unsigned int*)(VCORE_MBOX+0x0))
+#define MBOX_POLL       ((volatile unsigned int*)(VCORE_MBOX+0x10))
+#define MBOX_SENDER     ((volatile unsigned int*)(VCORE_MBOX+0x14))
+#define MBOX_STATUS     ((volatile unsigned int*)(VCORE_MBOX+0x18))
+#define MBOX_CONFIG     ((volatile unsigned int*)(VCORE_MBOX+0x1C))
+#define MBOX_WRITE      ((volatile unsigned int*)(VCORE_MBOX+0x20))
+#define MBOX_RESPONSE   0x80000000
+#define MBOX_FULL       0x80000000
+#define MBOX_EMPTY      0x40000000
+
+#define MBOX_REQUEST    0
+
+/* channels */
+#define MBOX_CH_POWER   0
+#define MBOX_CH_FB      1
+#define MBOX_CH_VUART   2
+#define MBOX_CH_VCHIQ   3
+#define MBOX_CH_LEDS    4
+#define MBOX_CH_BTNS    5
+#define MBOX_CH_TOUCH   6
+#define MBOX_CH_COUNT   7
+#define MBOX_CH_PROP    8 // Used for ARM to GPU
+
+/* tags */
+#define MBOX_TAG_GETSERIAL		0x00010004
+#define MBOX_TAG_GETARMMEM		0x00010005
+#define MBOX_TAG_GETVCOREMEM	0x00010006
+#define MBOX_TAG_GETCORETEMP	0x00030006
+#define MBOX_TAG_GETMAXCLK    0x00030004
+#define MBOX_TAG_GETCLK       0x00030047
+#define MBOX_TAG_SETCLK       0x00038002
+#define MBOX_TAG_LAST			    0
+
+extern volatile unsigned int mbox[36];
+//box should be 16 aligned.
+//mbox could be used for this.
+int mbox_call(uint8_t ch, volatile uint32_t *box);
diff --git a/uart.c b/uart.c
index 838708b..794dc5b 100644
--- a/uart.c
+++ b/uart.c
@@ -2,7 +2,6 @@
 
 #include "uart.h"
 #include "gpio.h"
-//#include "mbox.h"
 
 
 void init_uart(void )
diff --git a/utils.c b/utils.c
new file mode 100644
index 0000000..d8158f7
--- /dev/null
+++ b/utils.c
@@ -0,0 +1,54 @@
+#include <stdint.h>
+#include "uart.h"
+
+// K&R inspirated
+
+void printhex(unsigned int d)
+{
+	char n;
+	for(int c=28;c>=0;c-=4) {
+		// get highest tetrad
+		n=(d>>c)&0xF;
+		// 0-9 => '0'-'9', 10-15 => 'A'-'F'
+		n+=n>9?0x37:0x30;
+		putc(n);
+	}
+}
+
+int strlen(char s[])
+{
+	int i=0;
+	while(s[i]!= '\0') {
+		++i;
+	}
+	return i;
+}
+
+void reverse(char s[])
+{
+	int c, i, j;
+	for(i=0, j=strlen(s)-1; i<j; i++, j--) {
+		c=s[i];
+		s[i]=s[j];
+		s[j]=c;
+	}
+}
+
+void itoa(unsigned int n, char s[])
+{
+	int i=0;
+	do {
+		s[i++]=n%10+'0';
+	} while((n/=10)>0);
+	s[i]='\0';
+	reverse(s);
+}
+
+void printdec(unsigned int d)
+{
+	char s[16];
+	itoa(d, s);
+	for(int i=0; i<strlen(s); i++) {
+		putc(s[i]);
+	}
+}
diff --git a/utils.h b/utils.h
new file mode 100644
index 0000000..d3eda2f
--- /dev/null
+++ b/utils.h
@@ -0,0 +1,7 @@
+#pragma once
+
+void printhex(unsigned int d);
+int strlen(char s[]);
+void reverse(char s[]);
+void itoa(unsigned int n, char s[]);
+void printdec(unsigned int d);