Parts selection and operation to minimize the power consumption of desktop PCs

2021/3/30

Although power saving has been progressing recently, desktop PCs consume more than twice as much power as notebook PCs when idle and when working.I remember being shocked when I switched from using only a laptop computer to my own PC for the first time.

I will summarize the contents of my research on how to make a configuration that consumes as little power as possible even on a desktop computer.

CPU

  • The lower the TDP, the lower the maximum power consumption
    With intel, Core T series <Core SSeries <Celeron <Pentium <Core i3,5,7,9
  • Recent CPUs have a C-state function, so the power consumption at idle does not change.
  • There is a way to lower the minimum operating frequency and CPU voltage from the BIOS, but the hurdles are quite high.
    (Worst will not start)

It was surprising that even a high-end CPU is no different from a low-end CPU when idle.

The table below is a partial modification of "AKIBA PC Hotline!", But it can be seen that there is no difference at around 7W for i6700-6700K, 5T, i3, i22.5, Pentium, Celeron of the same generation. ..

Rather, the high-end CPU has a function to optimize the power management of the entire system (lowering the memory clock, etc.) when the load is low, and the Pentium and Core i series may save power when idle?
Comparison of i7 and Celeron in power consumption

Click here for C state ↓

You can put the CPU in low power mode to save energy when the CPU is idle.Each CPU has multiple power modes, collectively referred to as "C-State" or "C mode". (Omitted) Functions to cut the clock signal and power for idle units in the CPU.More power can be saved if more units are shut down due to clock cuts, voltage drops, or a more complete shutdown.

What is C-State?

The power-saving version with T or S at the end is difficult to obtain because it is rarely seen as a single part and is often sold as a built-in part.If necessary, it seems good to search by ok.

Motherboard

  • The higher the chipset, the higher the power consumption (see TDP of each chipset for details).
  • It seems that it will become smaller in the order of ATX> microATX> miniITX, but there is also an opinion that it is about an error
  • The more multifunctional onboard, the higher the power consumption

Onboard features can be dealt with to some extent by disabling them in the BIOS, and it's better than adding what you need later (Wi-fi, sound card, etc.) externally, so don't worry too much about it. ..

memory

-Using slow memory reduces power consumption (2133 <2666 <3600)
・ Rather than inserting two 8G cards, using only one 2G card will reduce power consumption.

It's a small amount, but if you stick to it, there will be a difference of about 10w. If you have a motherboard that can reduce the memory speed with BOIS, you can save power even if you have already purchased it.

Memory standard and power consumption
Quote: https://akiba-pc.watch.impress.co.jp/docs/sp/1083431-4.html

Any memory ...
I thoroughly verified the "real performance" of DDR4 memory from every angle

HDD / SSD

  • The smaller the number, the better
  • SSD (~ 5W) is overwhelmingly more energy efficient than HDD (~ 1W)

Graphic board (GPU)

  • If "configuration only for energy saving", survive with CPU built-in graphic
  • If you want performance, use a graphic board with as high a wattage performance as possible.
  • Recently, GPUs with semi-fanless design have also appeared.
  • Make it an external GPU (eGPU)

Since the power consumption of the GPU jumps up as much as it is mounted, I long for an external GPU (eGPU) that can be attached and detached as needed with a ThunderBolt 3 connection.However, the worst thing about COSPA is that it costs about 3 yen for the products below, so you can buy a graphic board by itself.

电源

  • Buy good 80 PLUS
  • Use power output that is about twice the power consumption during operation (about half of the power output has the highest power conversion efficiency).
  • Conversion efficiency is higher at 100V than at 200V (such as using an air conditioner outlet).
  • If your computer has a maximum of 150W, the AC adapter is the best.

Surprisingly, the AC adapter is excellent.

The 80 PLUS standard is "certification given to products with a power conversion efficiency of 80% or more in conversion from AC input to DC output".High efficiency in the order of standard <bronze <silver <gold <platinum <titanium (price is also ...)

The figure below shows the power conversion efficiency of the 100 PLUS gold power supply at 200V and 80V, but 200V has less loss or higher efficiency = power saving. The drawback is that 200V is not available.

SUPER FLOWER LEADEX III GOLD ARGB 550W conversion efficiency by voltage
Quote: https://www.tomshardware.com/reviews/super-flower-leadex-gold-550w-power-supply,4416-5.html

Fans

About fan related items such as case fans and CPU coolers

  • PWM mode is better than DC mode fan
  • Use a so-called fanless cooler consisting only of a heat sink
  • In some cases, the heat of the CPU is dissipated in the entire case.

Each fan consumes about 5-10W, so the less it is, the better.

Even a DC-controlled fan seems to save energy by rotating at low speed, but it seems that it consumes about 10% more power than a PWM-controlled fan because voltage loss occurs when adjusting the rotation speed.
Manufacture of fan controller for PWM control fan (1) What is PWM control?

Incidentally The case fan supreme seems to be made by Noctua.

There is a trade-off between energy saving and cost performance.