Tuesday, January 11, 2011

(Assembled is a series in which The Indian Geek is looking at how to choose the components for assembling your own home Desktop PC. This week's article is about motherboards)

Motherboard - exact

We’ve looked at which CPU you should buy, what graphics card would be best, and we’ve made the selection of a Hard Drive quite easy. Obviously, the motherboard comes next. First, let’s see what a motherboard is. It is the large circuit board onto which almost every single component of your computer is connected. Having said that, you must be able to guess that it’s also one of the most crucial components. It controls, co-ordinates, channels and transmits all instructions and data sent between the various components of the PC. A good motherboard should be able to do this quickly and efficiently as well as be able to handle a large variety of components.

In earlier days, motherboards used to handle only the processor (CPU), memory (RAM) and add-on cards. Anything else needed an add-on card. If you needed to connect a hard drive to it, you’d need a separate disk controller add-on card. As technology developed, more and more components were integrated in the motherboard. Disk controllers (IDE and then SATA and even RAID), Input/Output controllers (Serial, Parallel, USB), video controllers and audio controllers are some of the most common integrated components now-a-days. This not only make things a lot easier for us the consumers, it also reduces the cost considerably.

Motherboards generally consist of two main controllers, the north bridge and south bridge. These two together are what is known as the chipset. The north bridge is the faster of the two that controls the interfaces of the CPU, memory (RAM), the south bridge, PCI-E x16 slot, and in some controllers, the onboard video as well. The south bridge is slower and ergo, controls comparatively slower components such as the disk controllers (hard drive, optical drive), input/output controllers (mouse, keyboard, USB), onboard audio, etc.

Note: This is the traditional design of the motherboard. AMD has used a slightly different design for nearly a decade, which includes the memory controller within the CPU itself while Intel made the shift to a similar platform with the introduction of the 2010 Core family of processors. Many of Intel’s 2010 Core family of processors include a graphics controller as well, completely eliminating the need for a north bridge.

Since the options for purchasing a motherboard are plenty, we would like to explain the concepts surrounding the motherboard, and try to demystify the various factors that could (and should) influence your decision in picking the right motherboard.

ATx - CPU & fan

CPU Slot

We’re assuming that by this point you’ve already decided on which CPU would be powering your new assembled PC. Make sure the motherboard has the same slot. Both AMD and Intel have several types of slots. Intel currently has the LGA 775 (almost obsolete) , LGA 1366 (T), LGA 1156 (H) and LGA 1155 (H2). As far as we know, these are not interchangeable, meaning that no single processor will fit in more than one type of slot. Also keep in mind that the same family of processors may have different models that fit in different types of slots. There are several versions of the Intel Core i7 processor, some which use the LGA 1366 slot, some LGA 1156 and some LGA 1155. Please make sure you get the right slot. AMD currently has only two slots, the AM2+ and the AM3. AM3 slot processors are backward compatible, meaning that if you have an AM3 processor, it will fit in both AM2+ motherboards as well as AM3. This really comes in handy if you have an older motherboard and just want to upgrade your CPU. AM3 motherboards however, will not accept older AM2+ processors.

Chipset + Onboard Video

This is a very important component that is rarely given enough time and consideration. Since the chipset is what actually controls the flow of data between components, make sure you do your research before picking one. Both Intel and ATI have several chipsets for their processors. Some of the chipset’s features are easy to spot such as its support for DDR2 or DDR3 RAM, support for more than one PCIe x16 slots or just the presence of an onboard video controller. Some features are not so easy to notice such as bus speed, actual speed of the PCIe x16 slots run at and the type of video controller it has.

Since we recommended an AMD processor as the best option for a mid-range value-for-money all-in-one PC, we would like to mention a few AMD chipset options and their main features that sets them apart from other competing chipsets. AMD currently has the the latest 8 series and the previous 7 series. In the 8 series there are budget chipsets such as the AMD 880G which comes in MicroATX form, has good-enough onboard video (ATI Radeon HD 4250 ) and one PCIe 2.0 x16 slot. This is ideal for a value for money mid-range computer or an HTPC (home theatre PC). The AMD 870 is similar, but has no onboard video. The 890GX and 890FX are high-end models, the former supporting two PCIe x16 slots and the latter, four PCIe X16 slots.

Motherboard - circuitry

Supported RAM

Each motherboard chipset usually supports only one type of memory. The most common and current type is DDR3. While some DDR2 supporting motherboards are still available, we would not recommend buying one since DDR2 RAM is slower, increasingly hard to find and also expensive. Most mother boards have two, four or six slots for RAM modules. Smaller motherboards may have two slots to save space while high-end motherboards may have six slots for expandability and triple channel RAM. Most mid-range motherboards have only four slots. This usually enables upto 16 or 32GB of RAM in dual channels, depending on the motherboard. For the average user on a budget, four slots should be ideal.

PCI Express 2.0 x16 Slot

This is the fastest and largest slot on a motherboard and is used primarily for graphics cards. Now-a-days alsmost all motherboards will have at least one PCIe 2.0 x16 slot. Please don't mistake these with PCIe x4 or PCIe x1 slots which are slower, smaller and not for video cards. A few older motherboards that might still be availble may have a PCIe 1.0 x16 slot. These are slower and we would recommend avoiding them. If you don’t plan on getting a discrete graphics card, you probably will not need a PCIe x16 slot, but since all motherboard come with one, its good to have one in case you change your mind later, and would like to purchase an additional graphics card.

For those who are hell-bent on gaming and plan on upgrading soon, a board with two or more PCIe x16 slots might come in handy. Both ATi (Crossfire) and nVidia (SLi) allow you to use two or more graphics cards in parallel for about 1.5 to 2 times the performance. You could get a graphics card now, and later when you want to upgrade, get a second one. Please note though that your motherboard must explicitly support Crossfire or SLi; just the presence of two PCIe x16 slots does not mean they will work. Also, most motherboards with two PCIe x16 slots will only run at half speed (x8) when there are two graphics card installed. This however only has minor performance hits. Motherboards that can support two cards at full x16 each are usually very expensive and beyond the reach of the average consumer. Another thing to keep in mind is that the cards that you use must have identical GPUs, though they can be different board manufacturers. For example, an XFX ATi HD 4870 and a Saphire ATi HD 4870 will work fine in Crossfire, but a Sapphire ATi HD 4870 will not work with a Saphire ATi HD 5770. There are a select few non-identical combinations that might work, albeit at a reduced performance.

Additional Slots

The two types of add-on slots currently available are the older PCI and the PCIe x4. Your need for this depends on what add-on cards you intend on using. The most common ones are sound cards and TV tuner cards, though the latter has lately taken the USB form. Even if you don’t have any add-on cards now, we’d recommend having at least one available for future expandability.

Form Factor

Form factor refers to the overall dimensions of your computer’s case and therefore your motherboard as well. The two common sizes are ATX and MicroATX. ATX is the standard size that more desktop computers come in nowadays. An ATX motherboard will not fit in a MicroATX case. So if you plan to buy a smaller case or build your own HTPC (Home Theatre PC) for the living room, you will need a MicroATX motherboard. If you’re getting a standard-sized ATX case, you can choose from either. While MicroATX motherboards tend to be cheaper, they have smaller dimensions which limits the available expansion slots. Some may have only two RAM slots and maybe only one PCI and/or PCIe x4 slots. So if you’re a person who likes adding, changing and upgrading your computer, a full-sized ATX motherboard will give you better flexibly.


Another aspect to keep in mind is the layout of all the slots and components. In some motherboards, the RAM slots are right next to the CPU slot. This will be an issue if you plan to fit a large after-market CPU heat sink. Another common issue is the motherboard heat-sink getting in the way of add-on cards. Some boards have no space between the PCIe x16 slot and an adjacent slot (photo below). Most graphics cards have large heatsinks and not only occupy extra space, their cooling fans need room to breathe. We definitely cannot recommend a single layout that would be best; you will have to decide on a suitable layout motherboard, after deciding the add-on cards and other components that you would like to install in the PC.

We hope this article was helpful to de-mystify motherboards, and to help you decide which one to look for and buy. Feel free to respond in the comments section with your own opinions, thoughts and questions. And do watch out in the coming weeks for more articles in the Assembled series, which look at choosing the right RAM, keyboards and mice and other things that would make your assembled Desktop PC complete.

Other articles in our Assembled series:

Choosing the right CPU

How to choose your graphics card

Hard drives made easy

Selecting RAM, chassis case and Power Supply Unit



Nice article. I would have liked to see more regarding the specifications of MBs i.e. how to figure out the features of the motherboard looking at the technical specs. This will immensely help me as I am pondering over the cheapest and best AM3 Motherboard with support for all the above eg- sata 3, usb 3, dual channel, high fsb etc.

The Indian Geek said...

Hello Saiprasad,

Thank you for your feedback. We really appreciate it. It makes us happy to know our readers find our information useful.

The purpose of the Assembled series was to empower almost any Indian to make wise choices when attempting to build an Assembled PC. We tried mostly to keep the tech details to a minimum. (That was hard!)

For detailed info and possible reviews of specific motherboards (or other hardware components) we suggest that you visit a hard-core website such as Tom's Hardware or AnandTech.


mohan kumar said...

Dear Geek,
iam urgently seeking a rendering pc for my current project. i need opteron 6128 - 4 processors with a quad socket motherboard, like supermicro. here, the cpu prices are too high, and if i assemble the pc and bought from outside india, i can assemble this config within 90thousand. but, here in india, 1 cpu costs 18,000 and it totals 72thousand for 4 processors, whereas in US, the same 4 processors totals to 50thousand. I asked a nearby store here in chennai, but the storekeeper replied that, buying processors and assembling them outside india like from US will make trouble and wont work properly when used in India due to climate. Is there really such problems occur? please help me! Thnx.

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