FPSLabs : Motherboard Discussion

Christian "ZeGermans" Koebel checks in with a look at motherboards. ZeGermans describes how a motherboard is arranged architecturally, how it’s information is routed, and what types of things to look for in a motherboard, based on your needs and budget.

A few weeks ago we took a look at the inner workings and functionality of RAM. This week, we go over a much broader topic of another important (if not most important) part of your computer: the motherboard. To put it very simply, the motherboard is what ties every part of your system to another part. It links the RAM to the CPU to the video card to the sound card to the USB ports to Ethernet port and so on. This article will first detail how a motherboard is arranged architecturally, and how information is routed through it so it can reach every tip of your computer’s reach. Once that is out of the way, this article will also detail what types of things to look for in a motherboard, based on your needs and your budget.

Most modern motherboards consist of several different sockets for inserting nearly any type of device (CPU, RAM, video card), and two chips. These chips are known as the northbridge and southbridge. In some motherboards, you will find only one chip. This is due to the manufacturer combining both chips into one, which thus reduces the communication time between northbridge and southbridge. When referring to a motherboard’s chipset, one usually only refers to type of chip that the northbridge is using. Now you may wonder, "Why is it called a chipSET if it’s only one chip?" That is simply an error of motherboard marketing. An actual chipset is both the northbridge and the southbridge; for example: VIA K8T800 is merely a northbridge, whereas K8T800/VT8237 is a chipset. Why does common convention see the northbridge as the only chip worth mentioning? Well, this answer lies in the architecture of a motherboard.

The northbridge handles all major input/output devices. It handles communications between computer parts whose bandwidth is in the gigabytes per second. It could be considered more the ‘brains’ of a computer than the CPU is. The northbridges responsibilities differ slightly between Intel boards and Athlon64 boards. Therefore, both will be independently examined. On the Intel boards with most gaming setups, the northbridge will communicate with four major, bandwidth-hungry devices. The first is obviously the CPU. Any calculations or instructions relayed by the CPU go through the northbridge first, on their way to whatever part of the computer that they’ve been sent. The second is the RAM. If the CPU needs some sort of information out of the RAM, it sends the request to the northbridge which in turn uses its memory controller to retrieve the information from the RAM. It also sends information to be copied onto the RAM, which it receives from the hard drives, via the southbridge. This is its third duty. It handles all information sent from the south bridge that needs to be computed in some area of the northbridge’s jurisdiction. Its final job is to relay information from these other input sources to the video card. It sends the card textures and mouse movements from the southbridge, physics calculations and AI movements from the CPU, and other things. AMD64 northbridges are very similar, except the CPU has its own built-in memory controller, which cuts out the middleman between CPU and RAM. This format offers a vast increase in memory bandwidth and latency; however, it comes at a cost of upgradeability. If you changed RAM standards (DDR->DDR2 for example) you’d have to replace CPU, mobo, and RAM, as opposed to just mobo and RAM for Intel setups. Depending on your manufacturer, the northbridge will sometimes also handle the Ethernet port, though this task often falls on an independent chip. Due to the ever-increasing frequencies (and thus, bandwidth demands) of computer parts, almost all northbridges have at least a passive cooler and many higher-quality mobos have active coolers on their northbridges.{mospagebreak heading=Page 1&title=Page 2}
The southbridge handles the lower-bandwidth communications, dealing in the megabytes per second range. It controls and accesses all hard drives, optical drives, and floppy drives, both PATA and SATA. It also handles communications with the rest of the expansion slots that the northbridge doesn’t control, such as PCI and PCI-E 1x slots. It also gathers information from your USB and firewire ports. In general, it bundles up all the input from the lower-bandwidth devices and transmits it as a large bandwidth signal to the northbridge. The southbridge is almost never seen with an active cooler (unless part of a two-in-one chip setup with the northbridge), but some mobos include at least a passive cooler on it.

Now that you know all this about the motherboards, what should you look for in them? Well, that all depends on your needs. If you’re into overclocking, your best bet is to invest in a board that keeps voltages very stable, even if it’s increased, and one that offers large headroom in increasing the voltage. Also look for active coolers on the northbridge if you plan to squeeze some extra juice out of your PC. If you’re not an overclocker, however, these features aren’t worth the price you pay for them. For the average user, your best bet is to find a mobo that has plenty of SATA ports (a minimum of 4), offers at least 3 ram slots, and, preferably, offers PCI-E graphics support. The best northbridge available right now for AMD64 systems is the nForce4 ultra (or nForce4 SLI if you want to go that route…). For Intel, the best northbridge offered is the 925XE, but it will soon be replaced by the 955X which offers dual-core support.

Hopefully this article will help you know what to look for the next to you upgrade or buy a whole new computer. Next time, I will be writing about everyone’s favorite peripheral… graphics cards! Hope you enjoyed.

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