What Motherboard Do I Need?


Oct 26, 2000




Motherboards are as unique as the processors they support. When deciding on a motherboard it is necessary to understand certain specifications about motherboards as well as the processor you choose and the case you want to put it all in. I am writing this review to help clear some of the confusion of motherboard specifications.

AT or ATX

Most motherboards being made now are ATX form factor. The form factor is basically what type of power supply the motherboard uses and it orientation in the case. If you have an AT case, you can't put an ATX motherboard in it except for a few cases that support both types of motherboards by having a removable metal plate that can be replaced with a plate for the other form factor.

A standard feature of an AT form factor motherboard is the large keyboard interface, about inch in diameter and has 5 pins. AT form factor usually only supports serial mice, but some of these newer motherboards support PS2 mice with a special connector from the motherboard. ATX form factor supports the PS2 keyboard and mouse interfaces.

Some computer cases are proprietary in design so that you can't use either AT or ATX form factor motherboards. Older Compaq, Hewlett Packard, and Packard Bell computers are a prime example of this.

Slot who? Socket what?

Another defining factor of a motherboard is what type of processor it will support. Until 1999, this was not as much of a decision as it is today with the introduction of the AMD Athlon and the new Thunderbird and Duron processors. Most motherboards were either "Socket 7" or "Slot 1" which were the two dominant motherboards for supporting current processors like the Intel Pentium, Pentium II and Celeron as well as the AMD K5, K6, K6-2, K6-III and Cyrix processors.

Now the decision is a little more complicated. After you decide which processor you want, you can decide on what type of motherboard you need to support it. Here is a simple list of motherboard types and what processors they support.

1) Socket 7 - Pentium and Pentium MMX, Cyrix, AMD K5, and K6 up to 233MHz

2) Super Socket 7 - Pentium, Pentium MMX, Cyrix, AMD K5, K6, K6-2 and K6-III

3) Slot 1 - Pentium II, Celeron (Cartridge only) and Pentium III

4) Slot A - AMD Athlon (Cartridge only)

5) Socket 370 - Celeron (non-cartridge), Pentium III flip chip

6) Socket A - AMD Athlon Thunderbird and Duron only

Even though this list is fairly accurate, there are still some exceptions. Like, if you have an older Slot 1 motherboard that only supports up to a 66MHz bus, you will not be able to use a Pentium III processor on it because the Pentium III processors use a 100MHz bus and some even use a 133MHz bus. Most newer Slot 1 motherboards have the ability to support 66, 100 or 133 MHz bus.

What is a bus?

A bus is a device that moves data from one place to another much like the way people ride buses to get from place to place. The bigger the bus, the more people can ride on it at the same time. This is the same for data buses. The front side bus of a motherboard transfers data from the cache memory to the processor. The wider the buses bandwidth the more data can be transferred per clock cycle.

For example, a 400MHz processor on a 66MHz bus processes data at the same speed as a 400MHz processor on a 100MHz bus. The processor on the 100MHz bus is able to process more data without having to go back to the cache memory for more data, therefor more data is processed per clock cycle. Speed is a by-product of the higher bus, the processor is really not faster but the data gets processed faster because of the bus.

What is AGP?

AGP stands for Accelerated Graphics Port and was designed for graphics cards. The first graphics cards were made to be used in ISA slots, then later came the PCI graphics cards and now we have AGP. ISA graphics cards were either 8-bit or 16-bit cards and were not capable of 3D graphics. The ISA bus was not capable of handling the amount of data needed to perform in 3D and the cards were not designed for intensive 2D accelerated graphics.

PCI graphics cards made the break into 3D acceleration and high performing 2D acceleration. The first of these cards were 32-bit and later 64-bit. These cards also added more memory in most cases to ease the load on the system main memory. The PCI bus runs at 33MHz on most motherboards but can be overclocked if you know how.

AGP introduced 128-bit cards that could perform 2D and 3D acceleration in quality that was previously unobtainable. The AGP bus on most motherboards run at 66MHz and can also be overclocked, but you should not attempt this unless you are extremely familiar with overclocking and the motherboard you are using.

What about memory?

Memory is a term that is overused and misunderstood many times. A motherboard has slots for main memory or RAM that is used by the operating system and programs. There are other types of memory that are just as important.

Cache memory is memory that used the most by the processor, if the data the processor needs is not in the cache it will go to the main RAM to find it. Cache usually comes in two levels, L1 (level 1) and L2 (level 2). Some motherboards even use L3 or level 3 cache.

Most processors today have a large amount of L1 cache built on the processor, so this really is not a motherboard specification but it is important just the same. The L2 cache usually resides on the motherboard near the processor, although many processors now have L2 cache on them as well. Some processors like the AMD K6-III have L1 and L2 cache on the processor and the motherboard has the L3 cache. The same motherboard with an AMD K6-2 processor would only have L2 cache on the motherboard because the K6-2 processor only has L1 cache on the processor.

Main memory or RAM is Random Access Memory and is mostly used to store volatile information for the operating system or programs in use. The first 640k of main memory is called Conventional memory and is used more for running programs than data storage for programs. The first 64k of the conventional memory is called High memory and this is where the operating system kernel and some important drivers are stored while the computer is in operation.

I hope this helps to clear some of the confusion surrounding motherboards and their specifications. If you have any questions, you can email me and I will answer in a timely manner.

Thanks for reading,
Gr8ful :-)


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