--- a/doc/os.rst	Fri Feb 20 14:25:35 2015 +0100
+++ b/doc/os.rst	Fri Feb 20 15:47:54 2015 +0100
@@ -1,6 +1,34 @@
 OS
 ==
 
+Implementation
+--------------
+
+Arm
+~~~
+
+Vexpress-a9
+
+
+For the first implementation the qemu arm system vexpress-a9 machine was
+targeted.
+
+To launch this machine with a kernel use:
+
+.. code::
+
+  qemu-system-arm -M vexpress-a9 -m 128M -kernel kernel/kernel_arm.bin \
+    -serial stdio
+
+The memory layout of this image is as follows:
+
+- 0x00000000
+- 0x10000000 : hardware.
+- 0x10009000 : pl011 --> the uart peripheral
+- 0x60000000 : bootloader of qemu itself.
+- 0x60010000 : main memory, where kernel is loaded by the bootloader.
+
+
 Design
 ------