OK here it is.
The processor communicates with the rest of the system via the system bus. Back when desktop computers first came out, the processor worked at the same speed as the rest of the system. Of course back then, processors were relatively simple beasts that did not have a whole lot of circuitry in the package. In fact, what we now think of as a processor was several chips scattered across the motherboard.
Throughout to 80’s, as computers were improved, each new generation of processor would integrate some of the functions that had previously been located on the other chips. At the same time, new ideas for circuitry were coming out at a fair pace (at 16mhz, on the motherboard is just as good a location as on the processor). Beginning with the 80486 processors that were the big guns at the end of the 80’s, processors now had enough circuitry to do useful work twice as fast as the motherboard. At the same time, motherboard manufacturers were hitting some technical hurdles to making their products faster. Intel’s response to this was to start cranking out 66mhz chips that could run on 33mhz boards.
Today, the development cycle is still going on and modern processors can do useful work at ten or twenty times the speed of the motherboard. On die memory controllers are one of the next big things. Down the road a way for the desktop, today’s supercomputers are using ram chips that have processor circuitry built in (PIMRAM chips will try to keep the RAM organized so that the next data the processor is likely to request will be positioned in the chip for the fastest possible data retrieval).
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