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Low power computing at 8 watt idle

05 May 2021 - by 'Maurits van der Schee'

I've built another PC. This time I wanted to create a low power computer that could be always on. It aims to replace my NUC i7 with something powerful, silent and not too expensive. I've chosen an ASRock J5040-ITX motherboard with a on-board Intel J5040 CPU in an Inter-Tech ITX-601 HTPC case. This little machine is 3.2 GHz quad core with 32 GB of RAM a 1 TB SSD and costs less than 500 euro. It is a small, pretty, super fast and not too noisy little box. The case is an amazing value at 61 euros as it comes with a 60 Watt power supply with a power brick and all cables required. I run Xubuntu 20.04 LTS and it works great, I'm very pleased with the results!

ITX-601 with wifi kit

List of materials

The materials used in this build:

 61 Inter-Tech ITX-601 HTPC case
132 ASRock J5040-ITX motherboard with CPU
164 Crucial DDR4 SODIMM 2x16GB 2666
 90 Crucial P1 1TB M.2 Nvme SSD
 16 Scythe Kaze Flex 120 Slim fan
  8 Low Profile PCI-E x1 NGFF NVMe Adapter
 24 Intel Wi-Fi 6 (Gig+) Desktop Kit
--- +
495 Total

ITX-601 with 120mm fan

When you enable "CPU SpeedStep" and "CPU Turbo" in the BIOS this becomes both a very powerful and energy efficient machine. These settings allow the CPU to run between 800MHz and 3.2GHz depending on the load. You can bolt the Scythe 120 mm "slim" fan to the side/top panel (above the CPU). You need a 120 mm slim (15 mm height) case fan as there is not enough clearance to fit a normal 120 mm (25 mm height) case fan. You may have to use an awl to widen some of the holes in the panel (as fitting a case fan is not designed). Then you can connect the fan to CPU fan header on the motherboard. In the BIOS you can set the CPU fan to "Custom Speed" and configure "55" (from the 0-255 range) as its speed to have plenty of airflow and almost zero noise. I highly recommend this as an always-on (or HTPC) server, as it runs at 800 MHz and uses only 8 watt (on the socket) when idle. Under full load the system uses 30 watt and feels pretty fast with CPU temperatures around 60 degrees Celsius.

Wifi antenna and PCIe card

As you can see on the pictures I added the "Intel Wi-Fi 6 (Gig+) Desktop Kit", which can be connected to the motherboard's M.2 NGFF Wifi slot. Although there are holes that fit the antennas, one of the antennas (antenna pigtail connector) interferes with the PCIe card that holds the NVMe drive. This low profile PCIe card is fitted in the PCIe 2.0 x1 slot of the motherboard. With some gentle pushing it all fits, but only barely, so be warned.


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