| What does it do?
The Central Processing Unit CPU, or just ‘processor’ is the heart of your Mac, and actually does all the calculations and other processing of data. Old Macs used Motorola processors in the 68000 series, such as the 68040, and are known as ‘68K’ models. These were succeeded by the early Power Macs, using PowerPC 601, 603 and 604 processors, which are much faster but run quite different program code. All current models use third- or fourth-generation PowerPC processors, thus being G3 or G4 Power Macs, with the latest minitower models offering two G4 CPUs running at the same time. How does it work?
The CPU works on data brought into memory. Faster processors, including all PowerPC models, use temporary areas of memory which are much faster than regular memory, to buffer or cache both data and processor instructions. These instructions the program code might tell the processor to get a number from a certain address in memory, multiply it by another number, and then save the result to another address. PowerPC processors are designed to perform more than one instruction at a time, which makes them very fast. What can go wrong with it?
Most CPUs are now very reliable, although there are rare hardware failures which can occur if the CPU is driven too fast or runs too hot. Processor problems, ‘crashes’, almost invariably result from software errors for instance, the instructions in memory could be corrupted because of a bug, and the processor could then end up trying to use a chunk of data as if it were instructions. It will then enter an error state, and either your Mac will freeze, or Mac OS will detect the error and inform you. How can I upgrade it?
Upgrading processors varies considerably between Macs. In some, expensive motherboard replacements are available, but these are much less common now. Older Power Macs had their CPUs on small daughterboards, which can be replaced with faster versions. Most recent models allow you to actually swap the processor itself, although that is best performed by an engineer. Not all Macs can be upgraded so easily, though, and often it’s better to replace the whole computer. Further info
Web sites with further information include: support.info.apple.com/info.apple.com/applespec/applespec.taf a complete database of specs for all Macs; www.xlr8yourmac.com Accelerate Your Mac!, an excellent collection of info and resources for making your Mac faster. | |
