Hardware Reference
In-Depth Information
he voltage adjustment settings have upper and lower limits of 8 and -16, equivalent to 0.2
V above stock voltage or 1.4 V absolute and 0.4 V below stock voltage or 0.8 V absolute. he
voltage must be adjusted in whole numbers, and it cannot be adjusted below 0.8 V (-16) or
above 1.4 V (8.)
he following settings are accessible from
config.txt
:
❍
over_voltage
—Adjusts the BCM2835's core voltage. Values are given as a whole
number (an integer) corresponding to 0.025 V above or below the default value (
0
,)
with a lower limit of
-16
and an upper limit of
8
.
❍
over_voltage_sdram
—Adjusts the voltage given to the memory chip on the Pi. As
with
over_voltage
, values are given as a whole number corresponding to 0.025 V
above or below the stock (
0
,) with a lower limit of
-16
and an upper limit of
8
.
Additionally, you can adjust voltages for individual memory components using the fol-
lowing options:
•
over_voltage_sdram_c
—Adjusts the voltage given to the memory controller.
Acceptable values are the same as with
over_voltage_sdram
.
•
over_voltage_sdram_i
—Adjusts the voltage given to the memory's input/out-
put (I/O) system. Acceptable values are the same as with
over_voltage_sdram
.
•
over_voltage_sdram_p
—Adjusts the voltage given to the memory's physical
layer (PHY) components. Acceptable values are the same as with
over_volt-
age_sdram
.
As an example, the following lines entered into
config.txt
will give the BCM2835 a small
boost of 0.05 V to 1.25 V and the memory chip a bigger boost of 0.1 V to 1.3 V:
over_voltage=2
over_voltage_sdram=4
As with other settings, deleting the lines from
config.txt
or deleting the ile itself will
return things to normal. Unlike the other settings in this section, however, the evidence will
remain in the form of a blown fuse in the BCM2835—rendering the Pi's warranty null and
void even after the default settings are restored.
Disabling L2 Cache
he Pi's BCM2835 SoC processor has 128 KB of
Layer 2 cache memory
onboard. Although this
memory is small, it's extremely fast. It's used to temporarily store—aka
cache—
data and instruc-
tions between the slower main memory and the processor itself to improve performance.
