Motherboards

• What is a motherboard?
• Differences between motherboards
• The parts - processors
• Socket formats
• Intel processors
• AMD processors
• Dual processors and dual-core processors
• Chipset
• Choosing a chipset
• Memory support
• Hard drive support
• Peripheral devices
• Expansion slots
• Integrated interfaces
• Motherboard form factors
• The functions - BIOS and POST
• Questions
• Questions to ask the retailer

When deciding on the chipset to use in your system, you need to consider several factors. Which processors run with it and how much RAM will it support? Does it support PCIe (PCI Express)? Will it support the parallel ATA (PATA) for your older hard disks?

You also need to find out which functions are handled by the chipset - for example, integrated graphics. This saves money and is good for consumers who are not interested in high-level graphic detail, effects and speed, but is to the detriment of future upgrading if there's no AGP or PCIe slot on the motherboard (more on this later).

Like processors, memory technology has experienced a period of turbulent design, evolving through many different forms. Up until a few years ago, 72-pin SIMMs (single inline memory modules) were the norm, seen coupled to Pentium processors.

Next came DIMMs (dual inline memory modules), which only require one module to be used at a time, and are compatible with current SDRAM and DDR (double data rate) technology. You can put as many DIMMs in your PC as your motherboard has memory slots. You can mix and match DIMMs, so if your motherboard has two memory slots, you could put one 512MB and one 1GB memory module in, for a total of 1.5GB of memory.

DIMMs come in different flavours -- PC100 and PC133 for SDRAM, and PC2100, PC2700 and PC3200 for DDR SDRAM. The numbers relate to the speed at which they can operate (although the DDR numbers use a different measuring system).

Nearly all memory you buy now will be DDR memory. The most common type of memory available, and the type that nearly all new motherboards support, is PC3200, which runs at 400MHz. You can get 512MB of PC3200 DDR SDRAM for about $70 now.

If you have a new Pentium 4 motherboard, however, the chipset might be able to support the faster DDR2 memory. DDR2 increases the clock rate of the memory, and therefore, the speed at which the computer's processor can withdraw data from the memory. You can get 512MB of 533MHz DDR2 memory for about $110 now. It's more expensive than the 400MHz PC3200 memory, but well worth the extra money.

You may also see some versions of SDRAM advertised as ECC SDRAM. The ECC stands for error checking and correction and basically describes a process of checking data for errors and correcting them "on the fly". For instance, RAID is a form of error correction (see RAID explanation below).

Error correction works on the following principle: when a unit of data is stored in the system's RAM, a code that describes the bit sequence in the unit is created and stored alongside it. When the system goes to retrieve this unit of data, another code is calculated, which is then compared with the original code.

If the codes match, the data is sent. If the codes don't match, the missing or problematic bits are determined through the code comparison and supplied or corrected. The data that is still in storage is left uncorrected, hopefully to be replaced by new data.

If the error continues to occur in the same place after the system has been turned off and on again, the detection technology records the problem as a hardware fault.

ECC SDRAM is used primarily in servers, so it probably won't influence which motherboard you should purchase for your desktop setup. You will also need a chipset, which supports ECC in order to reap the benefits of this technology. ECC memory costs considerably more than regular (non-ECC) memory.

The three main types of PC hard drive interfaces on a motherboard are the parallel ATA (Advanced Technology Attachment), also known as the IDE interface, the serial ATA (SATA) and SCSI (small computer system interface).

Most consumer motherboards you buy now will have a mix of parallel ATA (PATA)/IDE ports and SATA ports. Typically, you would use the PATA ports to plug your CD or DVD drives into, while you plug your hard disks into the SATA ports. The important thing is that your motherboard has interfaces that support your devices. Hard disks, for instance, come with either SATA or IDE attachments. You motherboard needs to have the right one for your hard disk (or visa versa).

A very few motherboards support the third connection standard -- SCSI. SCSI is fast and can support more devices, but tends to be more expensive than its counterpart and is difficult to set up.

EIDE/parallel ATA

The EIDE interface evolved from the IDE interface, which supported both CD-ROM and hard drives. This then became UDMA (ultra direct memory access), which evolved from DMA and provided faster maximum data rates. In general, motherboards have one or two UDMA channels. Each channel can support two devices (so if you motherboard has two EIDE ports, it can support up to four EIDE devices).

Up to UDMA33, a 40-pin cable was used for all drive connections. The next advance, UDMA66, required an 80-wire cable but was backwards compatible, in that it also used a 40-pin connector. To obtain a UDMA66 (or faster) connection, the motherboard and all devices you attach must support UDMA66.

Ultra-UDMA is also referred to as Ultra-ATA or EIDE, and typically will be advertised as Ultra ATA33, Ultra ATA66, Ultra ATA100 and Ultra ATA133.

Ultra-ATA 133 is the most common interface today, providing a peak data transfer of 133MBps.

Serial ATA

In addition to the above ATA ports, which are a parallel interface, newer motherboards now feature Serial ATA ports. Serial ATA is a replacement for PATA, being faster, easier to configure and using much less bulky cabling. SATA and PATA are likely to co-exist in motherboards for some time, however, as the older PATA is phased out.

SATA hard drives work with current operating systems and are software compatible with parallel ATA. Adapters can be used to plug parallel ATA drives into SATA ports, but these are not a sure thing and not all adapters work with all chipsets.

The biggest benefit of SATA is its increased data transfer rates. While the fastest performing parallel ATA drives offer data transfer speeds of 133MBps, SATA operates with a data transfer speed of 150MBps. SATA drives also take up less room within the PC case due to smaller cabling (making them great for use within compact systems), and are more effective than parallel drives for cooling.

You will find at least two Serial ATA ports on the latest motherboards, with most boards boasting four or more ports. Unlike PATA, SATA works on a one-port, one-drive basis, so you don't need to "daisy chain" drives as you do with PATA. With SATA, drives can be arranged in RAID configurations for up to two drives.

If the motherboard you are looking to purchase is enabled for SATA, it will be noted on the board packaging with the SATA working group's official logo, or in the motherboard manual.

If you're really a bleeding edger, you can look for motherboards that support the new SATA2 standard, which is technically capable of speeds twice that of SATA. With current drives, however, the speed of the interface is not the limiting factor (150MBps is more than enough to support the peak speed of any available hard drive), so the benefits of SATA2 will not be seen for some time. One major benefit of SATA2 is a feature called NCQ (native command queuing). This feature organizes the flow of data from the motherboard chipset to the hard drive controller in such a way that the hard drive does not have to stress itself too much when retrieving your data.

For example, if a set of data requests are sent at different times that are located near the centre of the hard drive, but there are also some requests within that group of data that are located on the outer edge of the disk, then the data requests will be organized so that all the requests for data near the centre of the drive are performed together and then the ones at the outer edge are performed together. This improves seek times as it cuts the amount of travel the hard drive heads have to go through. To benefit from NCQ, your hard drives need to support the SATA2 interface and so does your chipset.

SCSI

Pronounced "scuzzy", this interface allows users to connect up to 15 devices (depending on bus width) on a single SCSI port in a "daisy-chain" fashion. SCSI was originally developed by Apple and is supported by most operating systems.

SCSI has also been through a variety of evolution stages, from the original SCSI, now known as "plain" SCSI-1, right through to the latest Ultra-320 standard, capable of 320MBps transfer rates.

However, the increased performance and functionality of SCSI does come at a price: motherboards that feature dedicated SCSI ports are at the higher end of the spectrum, and are usually designed for servers.