Skip to main content

Upgrading And Repairing PCs 21st Edition: Processor Features

CPU Operating Voltages And Math Coprocessors (Floating-Point Units)

One trend that is clear to anybody who has been following processor design is that the operating voltages keep getting lower. The benefits of lower voltage are threefold. The most obvious is that with lower voltage comes lower overall power consumption. By consuming less power, the system is less expensive to run, but more importantly for portable or mobile systems, it runs much longer on existing battery technology. The emphasis on battery operation has driven many of the advances in lowering processor voltage because this has a great effect on battery life.

CPU Operating Voltages

The second major benefit is that with less voltage and therefore less power consumption, less heat is produced. Processors that run cooler can be packed into systems more tightly and last longer.

The third major benefit is that a processor running cooler on less power can be made to run faster. Lowering the voltage has been one of the key factors in enabling the clock rates of processors to go higher and higher. This is because the lower the voltage, the shorter the time needed to change a signal from low to high.

Starting with the Pentium Pro, all newer processors automatically determine their voltage settings by controlling the motherboard-based voltage regulator. That’s done through built-in VID pins.

For overclocking purposes, many motherboards have override settings that allow for manual voltage adjustment if desired. Many people have found that, when attempting to overclock a processor, increasing the voltage by a tenth of a volt or so often helps. Of course, this increases the heat output of the processor and must be accounted for with adequate cooling.

Note: Although modern processors use VID pins to enable them to select the correct voltage, newer processors that use the same processor socket as older processors might use a voltage setting the motherboard does not support. Before upgrading an existing motherboard with a new processor, make sure the motherboard will support the processor’s voltage and other features. You might need to install a BIOS upgrade before upgrading the processor to ensure that the motherboard properly recognizes the processor.

Math Coprocessors (Floating-Point Units)

Older CPUs designed by Intel (and cloned by other companies) used an external math coprocessor chip to perform floating-point operations. However, when Intel introduced the 486DX, it included a built-in math coprocessor, and every processor built by Intel (and AMD and VIA/Cyrix, for that matter) since then includes a math coprocessor. Coprocessors provide hardware for floating-point math, which otherwise would create an excessive drain on the main CPU. Math chips speed your computer’s operation only when you are running software designed to take advantage of the coprocessor.

Note: Most applications that formerly used floating-point math now use MMX/SSE instructions instead. These instructions are faster and more accurate than x87 floating-point math.