The Motherboard, Processor, and Memory - Buses, Slots, and Controllers
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The motherboard (Figure 2-1) is the ultimate telephone system. It lets all of the components of the PC, including the processor, memory, expansion cards, and all the controllers housed on the board itself, talk to each other at unimaginable speeds.
It does this through the use of buses, which are wires that carry data around the board:
- The AGP bus, which gives an AGP graphics card direct access to the system memory. It can store textures in main memory that it doesn’t have room for in its own local memory.
- The PCI bus, which carries data to and from expansion cards, such as sound cards, network interface cards (NICs), modems, and other PCI cards.
- The front-side bus (FSB), which carries data to and from the system’s CPU.
Figure 2-1
A typical motherboard
Each bus works at its own speed set by its controller, a logic chip that maintains the flow of traffic through its bus. The PCI bus operates at 33MHz on nearly every motherboard available today. The other two buses vary according to the motherboard you purchase.
The speed of the AGP bus is referred to in multiples of the original AGP specification. Currently, motherboards and graphics cards support both 4X and 8X AGP, but you’ll want to go with the latter. 4X AGP transfers data at 1066 megabytes per second, and 8X AGP cranks up its engines at 2100 megabytes per second (or 2.1 gigabytes per second). 8X AGP is just emerging at the time of this writing, but some benchmarks already show that it improves gaming performance in texture-heavy games such as Unreal Tournament 2003.
The FSB affects data headed to or returning from the CPU, which, of course, is the heart of the system. Current FSBs run at 400MHz or 533MHz for Intel Pentium– based computers, and 333MHz for AMD Athlon XP PCs.
Buses aren’t the only components dependent on the motherboard. Your choice of a motherboard will also determine your system’s expansion limits, its data transfer speed to the hard drive, and the range of special features offered by the board.
The motherboard houses both PCI and memory slots. The number of PCI slots it offers can be crucial if you purchase a number of upgrade cards. While most systems contain only a sound card and a network adapter or modem, there’s no telling what you may want in the future. You may decide to purchase a Small Computer System Interface (SCSI) adapter that would occupy another slot, a hardware MPEG (Moving Pictures Expert Group) decoder that would fill yet another vacancy, and so on. As a general rule of thumb, more expansion slots are better.
The AGP Slot Stands Alone: Don’t look for a motherboard with multiple AGP slots, even if you want a second display adapter. They do not exist. However, if you need multiple displays, most current video cards offer dual-display support.
It’s also nice to have free memory slots when you decide to upgrade your sys-tem’s RAM. You can do two things to ensure that you don’t have to pull a module to insert a larger one. (When you’re reduced to doing that, you’ll end up with a perfectly good memory stick sitting on a shelf.) First, buy one large module to start with when you first build your PC. Second, buy a motherboard with plenty of memory slots.
Various motherboards offer wide ranges of features. Some have onboard audio solutions—but don’t be concerned with them because they pale in comparison to high-end sound cards.
Stuff that you might want includes the following:
- A serial ATA controller - This interfaces with fast serial ATA hard drives. (Storage is discussed in Chapter 5.)
- USB 2.0 ports - USB 2.0 is much faster than its predecessor, USB 1.1. Devices such as external CD-RW (CD-rewritable) burners are already available for the new USB standard.
- FireWire ports - These ports are especially useful if you’re into digital video editing. Most digital camcorders interface with FireWire, allowing for speedy transfer of video to and from your PC.
- IDE RAID RAID - (for Redundant Array of Independent Disks) offers two advantages: speed and security.
- Other features - Card readers, integrated Ethernet, and the capability to tweak and overclock the board.
 This chapter is from Build Your Own High Performance Gamers' Mod PC, by Chen and Durham (McGraw-Hill/Osborne, 2004, ISBN: 0072229012). Check it out at your favorite bookstore today. Buy this book now. |
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