Boot - Raspberry Pi System Software Reference - page 27

Boot Delay
The boot_delay and boot_delay_ms options allow the user to reconfigure the delay used
by start.elf prior to loading the kernel. The actual delay time used is computed from
the following:

D =´+ 1000 b m

where

• D is the computed delay in milliseconds.
• b is the boot_delay value.
• m is the boot_delay_ms value.

boot_delay (b) Description

1 Default

The boot_delay_ms augments the boot_delay parameter.

boot_delay_ms (m) Description

0 Default

Avoid Safe Mode
A jumper or switch can be placed between pins P1-05 (GPIO 1) and P1-06 (ground) to
cause start.elf to initiate a safe mode boot. If GPIO 1 is being used for some other I/O
function, the safe mode check should be disabled.

avoid_safe_mode Description

0 Default (check P1-05 for safe mode)

1 Disable safe mode check

Overclocking
According to the Raspberry Pi Configuration Settings file, Revision 14
( http://elinux.org/RPi_config.txt ) the ARM CPU, SDRAM, and GPU have their own
clock signals (from a PLL). The GPU core, H.264, V3D, and ISP all share the same clock.