Articles: Mainboards

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PCB Design and Functionality

Our initial goal was to find a worthy rival to Intel P45 Express among iP43 based solutions, so we had to make sure that all potential candidates have ATX form-factor. Then we narrowed down out selection using numerous criteria, such as South Bridge with RAID support, 8-pin ATX12V power connector, additional controllers and external connectors. The idea was to find a mainboard that wouldn’t be any different from an average iP45 based solution, except for the missing second PCI Express x16 slot, of course. As a result, Asus P5QL-E turned out the only model that met all these requirements. Although later on we found out that still not quite all of them were in fact met.

The current ATX 2.2 standard includes the whole bunch of technical specifications for mainboards. Namely, it should be 12” long by 9.6” wide or 305 x 244 mm. However, Asus P5QL-E turned out 20 mm narrower. Lack of free space on the PCB and the need to accommodate a lot of additional controllers could have forced the engineers to place a 24-pin power connector in the center of the board:

 While we were investigating this matter, we found out that mainboard makers refer to the required length of the PCB when they speak of complying with ATX form-factor standards. As a result, you can buy 305mm mainboards that will be 244mm, 224mm, 210mm or even 193mm wide. However, all of them will be considered ATX models, because this standard implies that the connectors are close to the storage device chassis. But we don’t have a choice and we will continue with our Asus P5QL-E mainboard. Now let’s take a closer look at the upper part of its PCB:

Besides the already mentioned inconvenient location of the 24-pin power connector, there is nothing we could really complain about in the upper part of the PCB. Probably the capacitors placed too close to the processor socket could prevent you from installing any specific cooling solutions with broad base plate. For example popular Scythe coolers that use universal VTMS retention system (Versatile Tool-Free Multiplatform System). Moreover, the pins from these capacitors hanging off the bottom of the PCB may make it difficult to fasten the cooler backplate, like the one we use with our Zalman CNPS9700 LED cooler.

As for the advantages, we should definitely mention 8-phase processor voltage regulator circuitry. Mainboards of this class usually have maximum four phases in this circuitry. Besides, they used low-resistance MOSFET transistors that allowed lower heat dissipation and power consumption even more. Asus used only solid-state capacitors with polymer electrolyte in the processor voltage regulator circuitry as well as on the rest of the mainboard.

The chipset North and South Bridges are topped with very uniquely shaped heatsinks. They work perfectly well when the system is operating in nominal mode, however during overclocking the North Bridge heatsink becomes scarily hot. You have to get some additional cooling for it, but how could you securely attach a fan to a heatsink of such beautiful but complex shape?

There is one definite advantage we should point out: a secure screw-retention for the chipset North Bridge heatsink that ensures full contact. There is an aluminum backplate on the bottom of the PCB that isn’t pressed fully against the board, but serves mostly retention purposes and in addition helps dissipate some heat.

If you look at the lower part of the PCB, besides one PCI Express 2.0 x16 slot, you will also see two PCI Express x1 slots and three regular PCI slots. Intel ICH10R South Bridge supports six Serial ATA connectors and RAID configurations. The additional JMicron JMB363 controller provides support for Parallel ATA devices.

At first we were curious about the LSI L-FW3227-100 controller that we haven’t yet come across before. It provided FireWire support. However, soon we found out that in 2007 Agere Systems Company was acquired by LSI, so this controller is none other but an analogue of a well-known dual-port IEEE1394A Agere FW322 controller, which we have already seen many times on mainboards from different vendors. Strange things do not end up here, though. Asus P5QL-E uses an eight-channel Realtek ALC1200 for the sound codec, but there was no info about it anywhere on Realtek web-site. The story of the gigabit Atheros AR8121-AL1E controller is also pretty mysterious. We only managed to fine a one year old press release on Atheros official web-site that told about the launch of an ultra-compact chip (48 pins at only 36 mm² size). At that time it was supposed to go into notebooks due to small geometrical dimensions and power-efficiency.

The connector panel looks up to all contemporary requirements. It features PS/2 ports for keyboard and mouse, six USB, one FireWire, one eSATA, network RJ45 connector, coaxial and optical S/PDIF and six audio-jacks. The outdated COM-port is not on the rear panel, but it is laid out on the PCB as a pin-connector. Although they had to move it in front of the PCI slots, because of lack of free space. Overall, you can get a better idea of the layout advantages and drawbacks by looking at the following component scheme:

2cm narrower PCB may actually result in huge savings during mass production, but in the end the user winds up with a board that cannot boast the best components layout. This is where most layout drawbacks actually come from. The lack of free space on the PCB, however, cannot explain the use of non-traditional controllers. Windows users have nothing to worry about, but you may encounter problems trying to find drivers for alternative operating systems such as Linux, for instance.

However, despite smaller dimensions engineers managed to equip Asus P5QL-E mainboard with a full range of contemporary features, including those implemented by additional controllers. Just take a look at the detailed list of its specifications and see for yourselves:

Not all the features are implemented in full. For example, JMicron JMB363 controller besides PATA can also offer support for two SATA ports, however, there is only one eSATA on the rear panel. But we shouldn’t complain, because there is no other Intel P43 Express based mainboard out there that could compare to Asus P5QL-E in terms of features and functionality. Extensive functionality should allow Asus P5QL-E to equally compete against a solution on the top Intel P45 Express core logic set. However, before we make any statements, let’s check out the BIOS functionality of the Asus P5QL-E mainboard.

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