PCB Design and Functionality

When engineers work on a high-tech multi-functional product like a mainboard, for instance, they often face a lot of uneasy choices. The things get even more complicated if we are talking about one of the top solutions like Gigabyte GA-EP45-DQ6, which is equipped with a lot of additional controllers. A quick glance at the board is not enough to tell if the layout is smart or not, if the PCB design is convenient or not. We will only be able to learn how good it is by taking the time to check out every detail. So, let’s proceed.

Despite the tradition, we are going to start our discussion of Gigabyte GA-EP45-DQ6 mainboard layout with its back panel. It is in fact pretty easy to confuse one board with another especially if they have been made by the same manufacturer, belong to the same product series and have a lot in common. However, you will most likely remember what back panel of Gigabyte GA-EP45-DQ6 looks like due to four RJ45 connectors implemented via four Realtek 8111C controllers integrated onto the board.

Besides that, there are keyboard and mouse connectors, 8 USB 2.0 ports, a coaxial and optical S/PDIF and six audio-jacks. The eight-Channel sound on Gigabyte GA-EP45-DQ6 is implemented via Realtek ALC889A codec.

By the way, there is some additional controller on the board between PCI Express x16 graphics card slots that may have to do with four network cards, because it is extremely hot. It is topped with a heatsink connected to the chipset cooling system with a heatpipe. The layout scheme gives a hint: as we see the PCI Express lanes do not go straight to the chipset North or South Bridge, but to some switch. The chipset has limited number of available PCI Express lanes that why an additional controller was necessary.

Since we have already mentioned a heatsink, let’s continue with the chipset cooling system on Gigabyte GA-EP45-DQ6 mainboard. BY the way, the same type of chipset cooling is used on Gigabyte GA-EP45-DS4 and GA-EP45-DS5 mainboards.

A couple of small stand-alone heatsinks at the front cover additional Serial ATA controllers. The chipset cooler starts with a flat heat-spreader on top of the controller between the PCI Express x16 slots. Flattened heatpipe leads from it to a not very tall heatsink on the chipset South Bridge. The second heatpipe starts here and leads to the base of a larger heatsink on the chipset North Bridge. Two more heatpipes originate from the middle of it. One of them leads to the heatsink over half of MOSFET transistors in the processor voltage regulator, while the other goes a little farther and ends in the heatsinks over the second half of transistors.

In my opinion, this is not the most correct design for the cooling system. The heatpipes doesn’t cool anything by itself. It simply transfers the heat from the place of origin to the spot where it could be best dissipated. In other words, ideally, one end of a heatpipe should be directly over the heat source, while the other end should go to the center of a cooling heatsink. However, as we see, this cooling system design leaves three main heatsinks (on the additional controller, chipset North and South Bridges) on their own without any support from the heatsinks in the processor voltage regulator circuitry.

Certainly, the first two heatsinks over the additional controller and chipset South Bridge cannot be large and tall, because they will be in the way of large graphics cards. Therefore, the heatpipe between them has to start and end in their base. But why does the second heatpipe starting at the South Bridge heatsink lead to the base of the North Bridge heatsink, and not to its center? And why do two other heatpipes start in the center of the North Bridge heatsink instead of transferring the heat away from its base?

Gigabyte mainboards use very aggressive CPU fan rotation speed management algorithm by default. If the CPU is not overclocked and is not running under heavy load, the fan doesn’t rotate at all most of the time and only in this case the heatsinks over MOSFET transistors start heating up. If the fan rotates, they are almost completely cold, because even a small airflow is enough to dissipate that little heat that they get. The three main heatsinks that need intensive cooling in the first place remain hot all the time in any work modes.