Shop OBEX P1 Docs P2 Docs Learn Events
Over Clocking Circuit with 6.25MHz Oscillator — Parallax Forums

Over Clocking Circuit with 6.25MHz Oscillator

spragucmspragucm Posts: 5
edited 2011-12-30 04:10 in Propeller 1
Hello All,
I've been reading post after post about how the Propeller can over clock using the 6.25MHz oscillator, but I haven't run across a schematic showing how to do it.

So, does anybody have a schematic and instructions (with guidance) detailing how to overclock the Prop?

Also, what about a schematic for overclocking to 120MHz?

Thanks in advance from this newbie to y'all pros :)

Comments

  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-12-29 18:17
    No schematic required.. Just change the xtal.

    There is a bunch of information about the subject here: http://propeller.wikispaces.com/Oscillator

    Welcome to the forums!

    OBC
  • spragucmspragucm Posts: 5
    edited 2011-12-29 18:26
    Thanks for the quick response. I was wondering about a schematic because people keep talking about cooling and different capacitors than those used with the 5MHz crystal. Does any of that matter? Have you overclocked without any changes except for the Xtal?

    If so..GREAT! I prefer KISS
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-12-29 18:33
    Many have no issues with the 6.00 and the 6.25 crystals. Swapping them out, then changing the speed values in the code.

    I'm the one who used the 14.31818MHz (common to VGA cards) for 114.5MHz.

    OBC
  • spragucmspragucm Posts: 5
    edited 2011-12-29 18:39
    Sounds good. Thanks
  • SapiehaSapieha Posts: 2,964
    edited 2011-12-29 20:00
    Hi spragucm.

    As it is me that started Over Clocking. My answer to You are.

    For stable functioning be sure You have decoupling capacitors (100nF) on all pairs of Propeller 2-for 40 pins and 4-for 44 pins.

    To that at last one 10-33uF tantalum on pair nearest Crystal pins.


    spragucm wrote: »
    Sounds good. Thanks
  • AleAle Posts: 2,363
    edited 2011-12-29 22:08
    And btw, for the time being, no extra cooling is needed, this is a Propeller!!!.
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-12-29 22:45
    spragucm: Welcome to the fabulous world of the propeller.

    You will not find a heat problem with the prop unless you supply incorrect voltages, shorts or similar. But the prop is actually quite resilient as many of us have found.

    Overclocking: The max I have attained, with special groundplanes and decoupling is 14.31818MHz PLLx8, but normally ship 6.5MHz (104MHz). Sapieha had one of my DIP boards running at 120MHz for months but I have never been able to get a QFP prop running above 14.31818MHz (114.5MHz) and have not entirely checked that speed anyway.
  • SapiehaSapieha Posts: 2,964
    edited 2011-12-30 04:10
    Hi spragucm.

    One thing I forgot mention.

    If You build Yours own PCB --- Don't forgot all capacitors needed for Voltage regulators.
    Read carefully Data sheets to them and don't omit any capacitor that are recommended in Data sheet to them.
Sign In or Register to comment.