This PC was built with the following objectives in mind:
-PC workstation with entry level performance (in 2010)
-without expensive components and high priced cooling solutions
-low noise
-low power consumption
-good reliability

In my project, I have considered a motherboard and a power supply that are supposed to run without fan (cooling by free air convection). I have chosen Intel D510MO embedded fanless mainboard. Analyzing the power consumption (including one 3.5" hard disk and an additional PCI network adapter), I found that a 110 W rated power supply is enough for this computer.

Motherboard - Intel Desktop Board D510MO (embedded):
- integrated (soldered onboard) 1.66 GHz Intel Atom D510 processor (2 cores, 4 threads) with a passive heat sink
- Intel NM10 Express Chipset
- support up to 4 GB DDR2 800 MHz memory
- integrated 1Gb/s Ethernet controller - Realtek RTL8111DL
- integrated video Intel GMA 3150
- integrated audio controller - Realtek ALC662
- integrated legacy I/O controller Winbound W83627TGH-I: two serial ports, one parallel port, PS/2 keyboard and mouse ports
- other interfaces: two SATA 3Gb/s ports, seven USB 2.0 ports
- one PCI slot (in the end, I have installed on it an additional network adapter: Intel PRO/1000 GT)
- one PCI Express Full-Mini Card Slot
- small form factor: Mini-ITX
- low power consumption
- low price

Power Supply - PPQ 1003B:
- 110 W rated power
- quad output (+3.3 V, +5 V, +12 V and -12 V)
- built-in active PFC function
- CE conformity
- switching frequency: 67 kHz
- 100% full load burn-in test with quality engineering test report
- open PCB power supply (without frame)
- short circuit, overload and overvoltage protection
- does not have a built-in voltage supervisor circuit (it is not compatible with TFX12V/SFX12V/ATX12V standards and this is a big disadvantage when it is used in PC applications)

Hard disk:
- the use of a solid state disk (SSD) is recommended. As an alternative option, a HDD can be used. My prototype was built with a Seagate ST250DM000-1BD141 250GB hard disk. Later I have replaced the HDD with a SSD Kingston A400 240GB SATA 2.5inch (figure 14).

Case:
- I have used an old slim aluminium enclosure, initially designated for other not finished project, which was lying around for many years. I have adapted this case to includes computer components. There is room inside for two 3.5" hard disks. Also this case acts as a heatsink for the hard disks. You can use any case you want: mini-ITX, ATX-desktop, minitower and so on, new or second hand. You have to find a possibility to mount the power supply and the motherboard in your case. Because the power supply and the case used in this project are non-standard for PC, I have used 12 mm metal hexagonal threaded spacers to mount all the components inside. The case is vertically positioned for better air circulation.

Fans:
- there are two fans in my project, first one is used for power supply and second one is used for mainboard. According to PPQ-1003 data sheet, with natural convection cooling, we can obtain only 70 W on continuous running. To obtain 100 W, we need a forced air cooling of 17 CFM at least. For that, I have used an ultra-quiet 120 mm fan made by Akasa: AK-183-L2B, 12V DC voltage rating, with 1400 rpm fan speed and 44.8 CFM airflow (nominal values). Because is no need for the nominal airflow, I have decided to supply this fan with a reduced voltage of 5V DC, which correspond to approx. 600 rpm. The airflow obtained is enough to keep the power supply board and the heatsink at reasonable temperatures. In this way, the noise level created by this fan is also decreased significantly.

The second fan is used to create an air flow for the motherboard (the heat sink of the processor and the RAM modules). The fan I have chosen is a MagLev ME60151V2-000U-A99 from Sunon (low acoustic noise level, high reliability, auto restart, dust resistant). This is a 12 V DC rated fan, but I have used 5 V DC as power supply for it. The fan acoustic noise level is also reduced by powering it with a lower voltage. (This fan can still work even if it is powered with 3.3 V.)

The motherboard has a fan output with PWM capability. According to my tests, in this particular case, to obtain a lower acoustic noise level, it is better to use a lower than nominal voltage for the fans power supply instead of using PWM. The only condition is to test the fans at these voltages, before using them in PC, to be sure that always start to rotate at power on.

I have performed some temperature measurements (figure 5 and 6, when the ambient temperature was 26°C and without heavy CPU usage). With fans stopped, CPU temperature was around 42°C and the power supply temperature around 57°C (close to the 60°C limit for this device). With fans running, the temperatures have been decreased to around 35°C for both CPU and power supply. Figure 7 was taken with fans running and ambient temperature close to 30°C.

Supervisor circuit board:
- the power supply I have used has no voltage supervisor circuit, so I had to build one. The schematic diagram of this circuit is in figure 11. It was designed by me. It includes a TL7705 integrated circuit to create the Power Good signal needed by motherboard. If you don't want to make the complete circuit which will test the minimum level for all the voltages (+5 V, +12 V, +3.3 V and -12 V), you can use a simplified one with only the TL7705 chip which will test for +5 V only. However, I recommend you to build the whole circuit.

Power Cables
- Figure 10 shows the schematic of the power cables between power supply, motherboard, voltage supervisor board, hard disk and other peripherals. The motherboard has a 2x12 pin connector for power supply (that requires TFX12V or SFX12V power supply), but with some workaround wiring you can use, as I did, a 2x10 pin connector (old ATX12V 1.0 or 1.3 standard). You can see the pin connections in the schematic drawing. In our design, I have used a single supply line for both +5 V and +5V SBY.

Additional network adapter
- the mainboard includes one LAN interface based on RTL8111DL chip. It will work good when this PC is used as a workstation with any Linux or Windows operating system. If you want to use this PC as a small server / router, it will be better if you will add a network adapter, like Intel Pro 1000 MT / GT or similar, with PCI interface (figure 13).

I have successfully tested on this computer several operating systems: DOS 6, Linux CentOS 5/6/7, RedHat Linux Enterprise 7, Windows XP/7/8/8.1/10 and multiboot configuration [3]. Remember, this was an entry level PC in 2010, there is no room for high performance. It was not built for gaming. For newer operating systems is slow.

I have also installed VMware ESXi 4.1. This distribution does not support RTL8111DL network interface. I have tested several linux drivers for this LAN interface in ESXi 4.1. Some of them worked, but I had network dropouts under heavy load in all configurations. D510MO is not listed in the VMware Compatibility Guide.

UPGRADE:
Mainboard D510MO was produced in 2010 and is no longer supported by newest Linux operation systems. To preserve the functions and keep the rest of the components, it is necessary to upgrade to a new board (figures 15, 16) with the same low power consumption of max 10 W TDP. I wanted a motherboard with serial and parallel ports to connect development tools. I made the upgrade with ASRock J4005B:
- integrated (soldered onboard) 2.00 GHz Intel Celeron J4005 processor (2 cores) with a passive heat sink
- chipset embed in CPU
- support up to 8 GB DDR4 2400 SO-DIMM
- integrated 1Gb/s Ethernet controller, Realtek RTL8111H
- integrated dual graphics output, D-Sub and HDMI ports by independent display controllers
- integrated audio controller, Realtek ALC887
- integrated Combo PS/2 mouse/keyboard port
- other interfaces: two SATA3 ports, five USB 3.1 ports
- serial port COM1 and parallel port (ECP/EPP support)
- one PCI Express 2.0 x16 Slot
- UEFI based motherboard, it has no Compatibility Support Module (CSM) for legacy BIOS

An Ethernet PCIe card with Intel 82574L chipset and an internal cable for two USB 3.1 ports were added to motherboard. The fan made by Akasa used for power supply is a good quality device, still have the noise levels low. The second fan MagLev from Sunon used for motherboard became noisy after a few years, so I have remove it. In figure 17 are the temperature measurements of the upgraded system air-cooled with only one fan when the ambient temperature was 25°C and without heavy CPU usage. Figure 18 shows a comparison table of Intel low power consumption CPUs.

Warning: The power supply of this computer is an open frame device. If you choose a similar model, be careful when you work with the case open. There are hazardous voltages inside and there is no barrier between hazardous voltage parts and your hands as in other ordinary computers.

Disclaimer: The information on this web site is provided "AS IS", without warranty of any kind. The author has made the best efforts to ensure the design and the information provided are reliable. Under no circumstances shall the author be liable for any direct, indirect, incidental, special or consequential loss, damage, expense or injury incurred or suffered which is claimed to resulted from use of this site, even if expressly advised of the possibility of such loss, damage, expense or injury, including, without limitation, any fault, error, omission, interruption or delay with respect thereto.

Links:
[1] - Intel D510MO motherboard
[2] - PPQ-1003 power supply
[3] - Multiboot computer system
[4] - ASRock J4005B motherboard