Saving Money with Linux

Saving Money with Linux: Explore the BIOS

Maximum Power Saving Mode – Changes in Detail

Power management is a feature allowing you to save energy by putting devices into states in which they draw less power (low-power states) at the price of reduced functionality or performance.

On the first page of this article we explained that we enabled maximum power-saving mode in the BIOS.

This makes various changes to settings in the BIOS. Here are these changes in detail:

PCI Express Native Power Management is enabled

This allows PCI Express devices to enter standby state.

PCI Express is a high-speed serial computer expansion bus standard. It is the common motherboard interface for personal computers’ graphics cards, hard disk drive host adapters, SSDs, Wi-Fi and Ethernet hardware connections.

Native ASPM is enabled

Active-state power management (ASPM) is a power management mechanism for PCI Express devices to garner power savings while otherwise in a fully active state.

DMI Link ASPM Control is enabled and set to L0sL1 / L1

This allows the DMI connection to the Platform Controller Hub (PCH) chipset to enter low power state to reduce power consumption.

The PCH controls certain data paths and support functions used in conjunction with Intel CPUs. These include clocking (the system clock), Flexible Display Interface (FDI) and Direct Media Interface (DMI).

ASPM is enabled and set to L0sL1

ASPM saves power mainly achieved through active-state link power management whereby the PCI Express serial link is powered down when there is no traffic across it.

L0 – All PCI Express transactions and other operations are enabled.
L0s – A low resume latency, energy saving “standby” state.
L1 – Higher latency, lower power “standby” state (optional).
L0sL1 – Activate both L0s and L1 support.

PEG – ASPM is enabled and set to ASPM L0sL1

PEG Link Mode (PCI Express Graphics Link Mode) is a feature available in the BIOS of some ASUS motherboards, which automatically overclocks the video card by a small amount.

Intel SpeedStep from Auto to Enabled

SpeedStep is a series of dynamic frequency scaling technologies built into some Intel microprocessors that allow the clock speed of the processor to be dynamically changed (to different P-states) by software. It reduces processor power consumption by automatically lowering frequency and operating voltage.

Intel Speed Shift Technology from Auto to Enabled

Intel Speed Shift technology also known as HWP (Hardware p-state) or Hardware Controlled Performance delivers quicker responsiveness with short duration performance shifts, by allowing the processor to more quickly select its best operating frequency and voltage for optimal performance and power efficiency.

CPU C-states from Auto to Enabled

In order to save energy when the CPU is idle, you can command the CPU to enter a low-power mode. Each CPU has several power modes, which are collectively called “C-states” or “C-modes.”

Each C-state has different power-saving levels and wake-up times. How many C-states are available depends on the processor. On our 10th Gen Intel processor, there are 10 C-states with the higher ones offering:

C8 – the L3 cache is flushed and power to the PLL is removed
C9 – the VCC input voltage is minimized
C10 – the CPU shuts down completely

Package C State Limit from Auto to C10

Package C-states, often referred to as PC-states or PCx, happen when all the platform cores agree to enter a specific C-state.

RC6 (Render Standby) from Disabled to Enabled

Render C-State (RC6) is a method designed to optimize the average power of the graphics engine while the rendering engine is work idle. RC6 is connected when the graphics rendering engine, the blitter engine and the video engine do not have an active load, and when graphic memory transactions are not performed.

Aggressive LPM Support from Disabled to Enabled

Aggressive Link Power Management (ALPM) is a power management protocol for Advanced Host Controller Interface-compliant (AHCI) Serial ATA (SATA) devices, such as hard disk drives and solid-state drives.

Pages in this article:
Page 1 – BIOS Changes
Page 2 – Maximum Power Saving Mode – Changes in Detail

All articles in this series

Saving Money with Linux
Getting StartedWe kick off the series with everything you need to start saving
Power SettingsWe look at the 3 different power settings and some useful open source tools
BIOSExplore changing settings in the BIOS to reduce power consumption
PowerTOPAnalyze power issues and receive optimization suggestions
Computer OffPower consumption when computers are off
GamingGaming doesn't have to be energy intensive
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