crystal frequency, machine cycle and speed of my PC

Discussion in 'Embedded Systems and Microcontrollers' started by PG1995, Apr 21, 2012.

  1. PG1995

    Thread Starter Distinguished Member

    Apr 15, 2011

    I have always wondered what that GHz thing means about the processors. They say it's speed of a processor. For example, my computer used 2 GHz processor. After reading some of the stuff about 8051 I understand a little what crystal frequency, machine cycle, etc. are. So, I presume 2 GHz is crystal frequency.

    As it says in the attachment that the 8051 could use crystal frequency from 4 MHz to 30 MHz. Suppose a 8051 MCU is first connected to a crystal with frequency 5 MHz and then the same MCU is connected to 30 MHz. Would there be a difference in terms of performance. For 5 MHz machine cycle would 2.4 μs and for the 30 MHz it would be 0.4 μs.

    If using a higher frequency crystal really raises the performance bar, then, theoretically speaking, can I use higher frequency crystal for my PC so that it perform well?

    Thank you.

  2. BillO

    Distinguished Member

    Nov 24, 2008
    Yes, higher frequency clocks will make the 8051 and your PC run faster.

    Going from 5 mHz to 30 mHz will increase the speed of the MCU by 6 times.

    Many PC enthusiasts increase the speed of their processor clocks, especially the game-heads. they call it overclocking. Look it up. However, keep a couple of things in mind.

    1) GHz clocks are not created only by crystals. The clock on modern PC is generated using fairly sophisticated methods. You can't just pop a faster crystal in there and expect it to work.

    2) You will never speed up a PC by a factor of 6!!! Maybe 4%-10%, if you are lucky.

    3) make sure the MB for the PC is capable of overclocking. It needs to be aware of this so that it can manage the speed of the memory and I/O buses in light of the increased CPU speed. Otherwise you'll run into timing issues and your PC will stop working.
  3. PG1995

    Thread Starter Distinguished Member

    Apr 15, 2011
    Many thanks for helping me with many queries related to microcontrollers which I posted about two days ago.

    Kind regards