Hardware Reference
In-Depth Information
consisted not of one but of several chips, all mounted on a daughterboard that was then plugged into a
slot in the motherboard. This worked well, but there were additional expenses in the extra cache
chips, the daughterboard itself, the slot, optional casings or packaging, and the support mechanisms
and physical stands and latches for the processor and heatsink. All in all, slot-based processors were
expensive to produce compared to the previous socketed versions. With the advent of the second-
generation Celeron, Intel began integrating the L2 cache directly into the processor die, meaning no
extra chips were required. The second-generation (code-named Coppermine) Pentium III also
received on-die L2 cache, as did the second-generation Athlon (code-named Thunderbird) processor
from AMD. With on-die L2 cache, the processor was back to being a single chip again, which also
meant that mounting it on a separate board plugged into a slot was unnecessary. All modern
processors now have integrated L2 cache (and most high-end processors from Intel and AMD also
have large integrated L3 cache) and use the socket form. As a bonus, on-die cache runs at full
processor speed, instead of the one-half or one-third speed of the cache in slot-based processors.
Chipsets
We can't talk about modern motherboards without discussing chipsets. The
chipset
is the
motherboard; therefore, any two boards with the same chipsets offer essentially the same level of
performance and features.
Depending on the model, the chipset may contain the processor bus interface (called front side bus, or
FSB), memory controllers, bus controllers, I/O controllers, and more. All the primary circuits of the
motherboard are contained within the chipset. If the processor in your PC is like the engine in your
car, the chipset represents the drivetrain and chassis. It is the framework in which the engine rests and
is its connection to the outside world. The chipset is the frame, suspension, steering, wheels and tires,
transmission, drive shaft, differential, and brakes. The chassis in your car is what gets the power to
the ground, allowing the vehicle to start, stop, and corner. In the PC, the chipset represents the
connection between the processor and everything else. The processor can't talk to the adapter boards,
devices, memory (in some models), and so on without going through the chipset. If you think of the
processor as the brain, the chipset is the spine and central nervous system.
Because the chipset controls the interface or connections between the processor and just about
everything else, the chipset ends up dictating which type of processor you have; how fast the buses
run; and in some cases what speed, type, and amount of memory you can use. In fact, the chipset might
be the single most important component in your system—possibly even more important than the
processor. I've seen systems with a slower processor but a better chipset outperform systems with a
faster processor, much like how a car with less power might win a race through better cornering and
braking. When deciding on a system, I often start by choosing the chipset, because the chipset
decision dictates the processor, I/O, and expansion capabilities.
Chipset Evolution
When IBM created the first PC motherboards, it used several discrete (separate) chips to complete
the design. Besides the processor and optional math coprocessor, many other components were
required to complete the system. These other components included items such as the clock generator,
bus controller, system timer, interrupt and DMA controllers, CMOS RAM and clock, and keyboard
controller. Additionally, many other simple logic chips were used to complete the entire motherboard
circuit, plus, of course, things such as the actual processor, math coprocessor (floating-point unit),
