Add a Fan to Resolve J3455B-ITX’s Heating Issue

My J3455 computer is quiet but runs hot in the tiny Mini-ITX case[1]. I decided to use a fan to improve air circulation to cool.

The Mini-ITX Computer
The case is about the size of the Mini-ITX motherboard.

Background Information

The J3455 Computer

The ASRock J3455B-ITX[2] is a tiny Mini-ITX motherboard (21.5 x 19.5 x 6cm) with an embedded Intel Celeron J3455. There is a heatsink on top of the CPU and use radiation for heat transfer.

Power is provided by a DC-DC ATX PSU[3] converter which is similar to picoPSU-80[4] and an external 60W (12V @ 5A) power adapter.


  • Up to 52°C while Chrome is loading 112 tabs.
  • 42 ~ 44°C after loading.
  • 46 ~ 48°C while checking emails and reading static pages.
  • 48 ~ 51°C while watching a YouTube video at 720p.

Power Consumption

12 ~ 23W at the wall for my scenario. 14 ~ 17W while watching YouTube.


Checking Emails and Catch Up News

I have less than 20 emails to read every day and drop an email about every month. Maybe it’s because I rely on LINE and Facebook Messanger for interactive communication.

Feedly is my primary tool to manage RSS subscriptions. There are about 300 headlines I need to have a quick glance every day. About 30 will be opened to a new tab to read when free.


Usually, there will be more than 50 tabs opened until finishing. A post needs one to several weeks to finish depends on the topic. Computers are shut down at night and all tabs will be reopened after login.

Software Development

For projects, configurations are done by a browser. VisualStudio Code is seldom used for coding.

On the other hand, for LAMP projects, VisualStudio Code is a must-have. Codes are run in a virtual machine. It would be a local VirtualBox or Virtualization Station[5] on QNAP TS-251[6].

20 to 50 tabs will be opened for reference during development.


  1. Power consumption should be less than 50W for general usage.
  2. System temperature should be less than 50°C for general usage.
  3. The CPU and case fans need to run quieter than my air purifier.


  • Seagate suggests the operating temperature range for a hard drive is between 5 ~ 50°C[7].


Three different system fans are used in these experiments. They are all installed on top of the  CPU heat sink.

Blower and fans photos
The blower will pull the accumulated heat away while a fan will push air to the sink.


Model Size Pin Bearing Type[8][9] RPM CFM
Blower SB-M[10][11] 6 x 6cm 2 Unknown 4,000 12
ADDA AD0312MX-G56[12][13] 3 x 3cm 3 Hypro[14] 9,000 3.78
AMR DFB501012M70T[15] 5 x 5cm 3 2 Balls[16] 4,500 8.4
  • For rotation speed, the 3-Pin female connecter model could report the current speed while 4-pin is managed precisely by command. All could be changed by giving a different voltage.
  • The 4-pin model sends PWM[17] (Pulse Width Modulation) signal through the control input wire to the motor drive circuit to manage the fan speed with higher accuracy.
  • Rewire the power connecter to change the output voltage (12V, 7V, 5V) to a fan.[18]
  • The 3-pin model may connect to the 4-pin male connector on the motherboard. Some may adjust the voltage to change the fan speed with low accuracy.[19][20]
  • Bearing type is related to the working temperature, lifespan, and noise of a system fan.


Test Model Observation
Blower SB-M It is fixed to the top case by cable ties[21] and won’t kiss the CPU heat sink. Accumulated heat will be pulled away.

It reduces the CPU temperature but is too noisy.

A 2-pin fan doesn’t have a signal line and therefore won’t be controlled by the BIOS/software directly. Use a resistor[22] to lower the voltage from 12V to 7V will decrease the fan speed.

It is fixed to the top of the heat sink by cable ties directly.

It reduces more CPU temperature than the blower but is too noisy.

This 3-pin fan would be controlled by the BIOS/software directly.

Two are linked together and fixed to the top of the hear sink by cable ties directly.

It reduces more CPU temperature than the others. There is no significant difference between using one and two fans. One is much quieter than two.

This 3-pin fan would be controlled by the BIOS/software directly.



  1. Fix two AMR DFB501012M70T to the top of the hear sink by cable ties directly.
  2. Connect one fan to CPU Fan on the motherboard. Considering connecting another to Sys Fan during summer if necessary.
  3. Set up the rule in [CPU Fan 1 Settins] in BIOS: when [Target CPU Temperature] reaches “45°C/113°F”, change the [Target Fan Speed] to “Level 1”.

Temperature and Power Consumption

J3455B-ITX is always less than 48°C in my scenario. Usually, 34 ~ 40°C when the room temperature is 25°C.

At-wall power consumption is 12 ~ 23W. The extra fan doesn’t take up too much.


  1. Shopee: [全新] ITX機殼 @台南可面交@
  2. ASRock: J3455B-ITX
  3. Wiki: Power supply unit (computer)
  4. Ituner Networks: picoPSU-80, 80w output, 12v input DC-DC Power Supply
  5. QNAP: Virtualization Station
  6. QNAP: TS-251
  7. Seagate: What is the normal operating temperature for Seagate disk drives?
  8. Wiki: Bearing (mechanical)
  9. Overclock: What is rifle bearing fan?
  10. 露天:12V DC 風扇 渦輪散熱風扇
  13. 小白的生活工廠:ADDA綠標 Hypro軸承3公分風扇(AD0312MX-G56)
  14. ADDA: HYPRO Bearing Introduction
  15. AURICS Technology Co.: DC BRUSHLESS FAN 50x50x10mm SERIES
  16. Wiki: Ball bearing
  17. Wiki: Computer fan control: Fan connectors
  18. Mobile01: [請益] 關於風扇降速的工具購買 (降壓線)
  19. PTT: [閒聊] 風扇接頭詳解
  20. Johnpam: 機殼後面排風扇是小3pin插頭,而主機板上是4pin插座,要再去買…
  21. Wiki: Cable tie
  22. Wiki: Resistor

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