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Exactly how many clocks does a Computer consists of and how do they synchronize with each other?
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Problem
I am currently trying to understand how Computers are arranged and organized internally (so that I can learn Assembly Language) through an online book called The Art of Assembly by Randall Hyde. Irrespective of whether or not I'll learn Assembly, I'm finding it difficult to understand exactly how is everything synchronized in the Computer. I'm currently at 3.2 - System Timing topic.
Below are my observations and the things I currently understand not only from the book but also from the things I learned through understanding computers in general.
Reading the book, I've came to understand that there are atleast 2 clocks in the whole system. One is the System Clock which makes one of the lines within the Control Bus go HIGH and LOW periodically. The CPU also has it's own Internal Clock which controls the operations which are done by the CPU. Now the Internal Clock should be in sync with the System Clock for the whole system to make sense which means the control line (which oscillates between low and high) should be connected to the CPU so that both the clock combine and act like a single clock. But then this happened:
The above snippet is from the PDF version of the same book.
I still didn't get confused after reading this. I perfectly understood that the Internal Clock just runs twice as fast as the System Clock which is fine. My confusion came when the Author mentioned the words "On a 5 MHz 8088/8086 CPU the memory access time..." and "On a 50 MHz 80486, the memory access time...". The question is, 'How can CPUs have their clocks running at certain frequencies when their Clock depends on the System Clock?'. 'Shouldn't their Internal Clock run at a certain multiple of the System Clock?'. I've also came across overclocking the CPU and stuff. 'Won't that make the Internal Clock of the CPU go out of Sync with the System Clock?'
Perhaps the main problem in understanding how everything is synchronized in Computer is the understanding of the word 'synchronized'. And al
Below are my observations and the things I currently understand not only from the book but also from the things I learned through understanding computers in general.
Reading the book, I've came to understand that there are atleast 2 clocks in the whole system. One is the System Clock which makes one of the lines within the Control Bus go HIGH and LOW periodically. The CPU also has it's own Internal Clock which controls the operations which are done by the CPU. Now the Internal Clock should be in sync with the System Clock for the whole system to make sense which means the control line (which oscillates between low and high) should be connected to the CPU so that both the clock combine and act like a single clock. But then this happened:
The above snippet is from the PDF version of the same book.
I still didn't get confused after reading this. I perfectly understood that the Internal Clock just runs twice as fast as the System Clock which is fine. My confusion came when the Author mentioned the words "On a 5 MHz 8088/8086 CPU the memory access time..." and "On a 50 MHz 80486, the memory access time...". The question is, 'How can CPUs have their clocks running at certain frequencies when their Clock depends on the System Clock?'. 'Shouldn't their Internal Clock run at a certain multiple of the System Clock?'. I've also came across overclocking the CPU and stuff. 'Won't that make the Internal Clock of the CPU go out of Sync with the System Clock?'
Perhaps the main problem in understanding how everything is synchronized in Computer is the understanding of the word 'synchronized'. And al
Solution
Modern processors tend to have more clocks than processors in the past, because that means when a part of the processor isn't used, it may be possible to switch off that part completely, including the clock, to save energy.
Clocks are often not synchronised, because synchronising and keeping them synchronised is expensive and complicated, and if you can make a part of the processor work correctly without synchronising its clock, that's overall cheaper.
Clocks are often not synchronised, because synchronising and keeping them synchronised is expensive and complicated, and if you can make a part of the processor work correctly without synchronising its clock, that's overall cheaper.
Context
StackExchange Computer Science Q#63449, answer score: 3
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