Hardware Reference
In-Depth Information
Memory Partitioning—start elf
Although the Raspberry Pi only has a single 256 MB memory chip, that memory can be
apportioned to the hardware in a variety of ways. he BCM2835 is split into two main sec-
tions: the general-purpose CPU and the graphics-oriented GPU. Both of these sections
require memory to operate, meaning that the 256 MB of memory on the Raspberry Pi needs
to be shared between the two. his split is controlled by a ile called start.elf .
he typical split is chosen by the maintainers of the Linux distribution installed on the Pi.
Some choose to split the memory straight down the middle, at 128 MB each for CPU and
GPU, ensuring that the graphics hardware can perform to its fullest potential. Others allow
the CPU to have a larger share in order to improve general-purpose performance.
he majority of distributions include three copies of start.elf in addition to the one that's
loaded when the Pi boots: arm128_start.elf , arm192_start.elf , and arm224_
start.elf (see Figure 6-2). hese three iles are identical except for one small change: the
amount of memory reserved for the BCM2835's CPU.
Figure 6-2:
he various
start.elf
iles in the
/boot
directory
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