Custom bootloader

This is the boot script for the olpc. It is normally ofund on the nand, in /boot.

Open firmware first searches for this file on a usb stick, then on a sd card, and finally on the nand. Below are found a commonly used script to allow for booting from a variety of locations.

Boot location

You need 3 things to boot, a boot-file a boot-device and a ramdisk. You can hose these on a USB, a SD or on the internal nand. You may even have the olpc.fth boot file in any of these places (in /boot/) and the first location it finds is the one it is going to use. The order for searching is USB -> SD -> nand so it is possible to make a bootable USB stick, and it will boot that when present, but it will boot the normal nand when it is removed. this is helpful for trying out unstable distro's as it doens't alter the internal memory at all.

The locations of these items with either be:

• sd:\ - SD card
• disk:\ - USB disk
• nand:\ - internal nand

Boot-file

The inputs needed for the boot file are:

• ro - assuming this means read only
• root - location of the root filesystem
• rootdelay - optional adds in a delay before booting
• console - sets up the console displaay
• fbcon - sets up some fonts

The rootfile is the main editable place it points to the root filesystem partition Usually

• /dev/mmcblk0p1 - SD card
• /dev/sda1 - USB stick
• mtd0 -internal nand

Boot-device

This is the location of the kernal that you wish to boot this line usually works to:

locator\boot\vmlinuz

for example to boot from SD

sd:\boot\vmlinuz

Ramdisk

This is the initial ramdisk used for booting. Usually:

locator\boot\olpcrd.img

example to boot from SD

sd:\boot|olpcrd.img

Sample menued bootloader to allow for selection of boot location

\ 
\ Uber bootscript for OLPC  Place in /boot as olpc.fth
\
cr
." 1 to boot from SD" cr
." 2 to boot from USB" cr
." 3 to boot from internal nand" cr
." 4 to boot alternate image from Nand" cr
cr
key dup drop dup dup
31 = if 
\ SD boot info
  " ro root=/dev/mmcblk0p1 rootdelay=1 console=ttyS0,115200 console=tty0 fbcon=font:SUN12x22" to boot-file
  " sd:\boot\vmlinuz" to boot-device
  " sd:\boot\olpcrd.img" to ramdisk
else 32 = if 
\ USB boot info
  " ro root=/dev/sda1 rootdelay=1 console=ttyS0,115200 console=tty0 fbcon=font:SUN12x22" to boot-file
  " disk:\boot\vmlinuz" to boot-device
  " disk:\boot\olpcrd.img" to ramdisk
else 34 = if 
\ Alternate boot image info
   " ro root=mtd0 console=ttyS0,115200 console=tty0 fbcon=font:SUN12x22" to boot-file
   " nand:\boot-alt\vmlinuz" to boot-device
   " nand:\boot-alt\olpcrd.img" to ramdisk
else 
\ Default into boot as sugar
   " ro root=mtd0 console=ttyS0,115200 console=tty0 fbcon=font:SUN12x22" to boot-file
   " nand:\boot\vmlinuz" to boot-device
   " nand:\boot\olpcrd.img" to ramdisk
then
then
then 
unfreeze
boot
\ end of script

overclock

You can also overclock your OLPC with the olpc.fth file. In order to accomplish this you need to set your timings before it loads the operating system. You must add some numbers to the forth stack and when write these registers using wmrsr. Shown below is a specific overclock frequency and that can be changed by altering the middle number to what you find below in the overclock table.

7de009e
5dd
4c000014
wrmsr

You then add in any specific booting information you want (see above).

XO-1 Overclock Settings in MHz; default is 433/166 (4d9)
CPU	Bus Speed
	133	166	200	216	233
333	3d3	4d3	5d3	653	6d3
366	3d5	4d5	5d5	655	6d5
400	3d7	4d7	5d7	657	6d7
433	3d9	4d9	5d9	659	6d9
466	3db	4db	5db	65b	6db
500	3dd	4dd	5dd	65d	6dd
533	3df	4df	5df	65f	6df
566	3e1	4e1	5e1	661	6e1