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Monday, July 1, 2002

Make CPU work faster

OVER the past 15 years, the power of microcomputers has increased dramatically. When people talk about computing power, they usually mean the speed with which the computer processes data. Therefore, more computing speed means faster processing. The circuitary design of a CPU determines its basic speed, but several additional factors can make chips already designed for speed work even faster. You must already be aware of some of these, such as CPUs, registers and the memory, cache memory, clock speed, data bus, and math coprocessor affect a computerís speed.

Registers The registers in the first PCs could hold two bytes16 bits-each. Most CPUs sold today, for both PCs and Macintosh computers, have 32-bit register. The size of registers, which is sometimes called the word size, indicates the amount of data with which the computer can work at any given time. The bigger the word size, more quickly can a computer process a set of data. A CPU with 32-bit register can process data twice as fast as one with 16-bit register.

RAM The amount of RAM in a computer can have a lot of affect on the computerís power. More RAM means the computer can use bigger, move powerful programs, and those programs can access bigger data files. More RAM also can make the computer run faster. The computer does not necessarily have to load the entire program into memory to run it, but the more of the program it can fit into memory, the faster the program runs. For example, with more RAM available, more of the operating system (OS) can be loaded from the hard disk at startup. If more of the OS can be loaded into RAM, then less files need to be swapped while the computer is running. The hard disk is slower than RAM, so less swapping makes for a faster computer.

Internal clock Every microcomputer has a system clock, but the clockís primary purpose is not to keep the time of day. Like modem wristwatches, the clock is driven by the piece of a quartz crystal. When electricity is supplied, the molecules in the quartz vibrate millions of times per second, a rate that never changes. The speed of the vibration is determined by the thickness of the crystal. The computer uses the vibrations of the quartz in the system clock to time its processing operations. So faster the speed of the clock, faster is the processing power. Today, the fastest PCs have clock speeds of more than 200 MHz.

Data bus The data bus is an electrical path that connects the CPU, memory and other hardware devices on the motherboard. Actually, the bus is a group of parallel wires. The number of wires in the bus affects the speed at which data can travel between hardware components, just as the number of lanes on a highway affects how long it takes people to get to their destination. Because each wire can transfer one bit at a time, an eight-wire bus can move eight-bits at a time, which is a full byte. A 16-bit bus can transfer two bytes, and a 32-bit bus can transfer four bytes at a time, meaning thereby, with a wider bus, the computer can move more data in the same amount of time (or the same amount of data in less time).

Address bus The address bus is a set of wires similar to the data bus that connects the CPU and RAM and carries the memory addresses. The reason the address bus is important is that the number of wires in it determines the maximum number of memory addresses. If the address bus could carry only eight bits at a time, the CPU could address only 256 bytes of RAM. Today, most CPUs have 32-bit address buses that can address 4GB of RAM. Some of the latest models can address even more.

Cache memory Moving data back and forth between RAM and CPUís register is one of the most time-consuming operations a CPU must perform simply because RAM is much slower than the CPU. A partial solution to this problem is to include a cache memory in CPU. Cache memory is similar to RAM, except that it is extremely fast compared to normal memory, and it is used in a different way. The cache speeds-up processing by storing frequently used data or instructions in its high-speed memory. Whenever the CPU requests information from the RAM, the cache controller intercepts the request and searches its own memory for the requested information. If the information is not there, the CPU retrieves the required data from the RAM and also sends a copy back to the cache. The next time the CPU needs the same information, the cache finds that information, and quickly sends it to the CPU, leaving RAM out of the loop. The speed of cache memory is nearly equal to that of CPU.

Math coprocessor Some computers speed up certain kind of processing by adding a match coprocessor to the CPU. A math coprocessor is a chip that is specially designed to handle complicated mathematical operations. Newer CPUs have math coprocessors built in. Earlier CPUs did not have them; so many users choose to upgrade their machines by adding them.