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Highest clock speed — Parallax Forums

Highest clock speed

sovsov Posts: 17
edited 2010-07-30 10:18 in Propeller 1
What is the highest clock speed for the propeller chip? Right now I got mine at 100mhz and I would want it to run faster, is that possible?

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iPhone expert

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-07-30 04:25
    Read the datasheet!!! There's a nice graph showing the highest clock speed for a given ambient temperature and power supply voltage. This was tested using an environmental chamber and the same test program. The maximum clock speed is temperature and voltage sensitive. You might have to refrigerate the Propeller to get it to run as fast as you'd like. I wouldn't suggest upping the supply voltage unless you're very familiar with PCB layout and voltage regulators since there's very little margin between the upper end of the supply voltage range and where the Propeller gets destroyed from too high a supply voltage. It doesn't take much noise on the supply lines to the Propeller to push the voltage seen at the chip above the damage point.
  • sovsov Posts: 17
    edited 2010-07-30 04:39
    What happens if I were to upgrade my 6.25 MHz external clock to something higher will that change the clock speed?

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    iPhone expert
  • Mike GreenMike Green Posts: 23,101
    edited 2010-07-30 04:46
    The same thing that happens any time you change the clock speed. It either works or it doesn't depending on what clock speed you're using, what ambient temperature is present, and what operating voltage you're using. You always have to change the clock speed constants in your program to match because the expected clock speed is recorded in the binary file for the compiled program for use with the CLKFREQ function which is used by many speed dependent objects. The bootstrap loader uses the clock mode constant to set the initial clock mode for your program when it's started although your program can change all of these once it's running.
  • potatoheadpotatohead Posts: 10,261
    edited 2010-07-30 04:53
    It's gonna work great at some speeds, and 100Mhz is pretty much known to work great in most ordinary conditions.

    Exceeding that might work great, with the chance of that happening dropping rapidly according to what you see in the data sheet.

    At some point, it will appear to work great! That's the hard part. Some things will perform, others won't, and it will just appear buggy.

    Then it doesn't work great.

    Be sure and test everything at the known solid clock before advancing the speed of it.

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  • Cluso99Cluso99 Posts: 18,069
    edited 2010-07-30 10:18
    It depends more on the layout and decoupling and bulk tantalum capacitors. My RamBlades are sold clocked at 6.5MHz (104MHz) and a 13.5MHz xtal (108MHz) is also supplied and although I have done preliminary testing I do not guarantee it will work. The maximum I got on the RamBlade was 14.31818Mhz (~115MHz). Sapieha has my TriBlade running at 15MHz (120MHz). Both designs were done with overclocking in mind.

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