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Meeting The Components (Cont’d)

Although most motherboards use MOSFET transistors on the voltage regulator section, some transistors are better than others. The best transistors are the ones with lower switching resistance – a parameter called RDS(on). These transistors produce less heat (16% less heat compared to traditional MOSFET, according to Gigabyte) and consume less power to its own operation, meaning higher efficiency (i.e., the motherboard and CPU will consume less power). They are physically smaller than traditional transistors. An easy way to differentiate the two is by counting the number of available terminals. Traditional transistors have three legs, with the center leg usually cut, while transistors with low RDS(on) have four or more legs and all of them are soldered to the motherboard. You can see the difference between the two by comparing Figures 7 and 8.

The voltage regulator circuit will have two transistors per “phase” or “channel,” one called “high side” and the other called “low side”. Cheaper motherboards instead of using one MOSFET driver integrated circuit per channel uses one extra transistor per channel to perform this function and thus such motherboards will have three transistors per channel (phase) instead of two. Because of that the best way to count and identify phases is by counting the number of chokes, not the number of transistors.

Some motherboards, especially the ones from MSI based on their “DrMOS” technology, will use one integrated circuit replacing the “high side” MOSFET, the “low side” MOSFET and the driver MOSFET, and therefore on such motherboards you will find one integrated circuit per phase and no transistor.

MOSFET transistorFigure 7: Traditional MOSFET.

MOSFET transistorFigure 8: MOSFET with low RDS(on).

The capacitors used on the voltage regulator circuit can be of the traditional electrolytic type or solid aluminum ones, and we’ve already shown the physical difference between them in Figure 2. Solid aluminum capacitors are better than regular ones as they do not swell or leak. If your motherboard uses regular caps, you should discover their manufacturers. Capacitors manufactured in Japan have the tradition of being immune to swelling, leaking and explosions. We have already published a detailed tutorial on how to identify Japanese caps and you should read it.

Each voltage output is controlled by an integrated circuit called the PWM controller. The motherboard will have one of this per voltage level, i.e., one for the CPU, one for the memories, one for the chipset, etc (most PWM controllers are able to control two independent voltage levels). If you look around the CPU socket you should be able to find the PWM controller for the CPU voltage, see Figures 2 and 9.Some motherboards have the PWM circuit running at a higher frequency, which reduces power loss (in other words, it increases efficiency, i.e., lowers the amount of power consumed by the motherboard/CPU). The manufacturer will clearly advertise this feature if your motherboard has it.

PWM ControllerFigure 9: PWM controller.

Finally we have a smaller integrated circuit called MOSFET driver. The voltage regulator circuit will use one MOSFET driver per phase (channel), so each integrated circuit will drive two MOSFETs. Cheaper motherboards will use another MOSFET in the place of this integrated circuit, so in motherboards that use this design you won’t find this integrated circuit and each phase will have three transistors, not two as usual.

MOSFET driverFigure 10: MOSFET driver.

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.