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fastest safe operating clock - overclocking — Parallax Forums

fastest safe operating clock - overclocking

IanMIanM Posts: 40
edited 2006-12-11 18:23 in Propeller 1
I've done a search but can't find anything, so apologies if this question has already been asked. What is the fastest over-clocking speed (ie internal clock) the prop can get to without resorting to cooling etc. I've seen Chips comments on the conservative nature of the 80MHz clock but can it run at higher speeds safely enough for non-critical applications not exposed to temperature extremes?

Many thanks, Ian

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Ian Mitchell
www.research.utas.edu.au

Comments

  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-12-10 02:50
    Each Propeller is different on it's max speed. For room temperature a typical Propeller can achieve somewhere in the range of 96 to 110 MHz, but not all Propellers can run at 110. 96 is a good number because most if not all Propellers can run at this frequency and this is 6MHz + 16xPLL.

    If you have 2 Propeller's you can use one to test the other's maximum speed by using the counter of one to generate the clock of the other.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
  • IanMIanM Posts: 40
    edited 2006-12-10 03:15
    Excellent, thanks Paul.

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    Ian Mitchell
    www.research.utas.edu.au
  • cgraceycgracey Posts: 14,133
    edited 2006-12-10 07:52
    Propeller chips are production tested at room temperature to 104MHz (6.5MHz·* 16). So, every part passed a functional test at that frequency. Before the part ever gets hot due to speed, it will just cease to operate properly. However, if you can actively cool it to something like 0 degrees C, you could probably run it pretty reliably at over 128MHz.

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    Chip Gracey
    Parallax, Inc.
  • IanMIanM Posts: 40
    edited 2006-12-11 00:01
    yeah, i saw the DLP-PROP uses a 6MHz clock so i assumed that was quite safe

    thanks Chip

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    Ian Mitchell
    www.research.utas.edu.au
  • Bill HenningBill Henning Posts: 6,445
    edited 2006-12-11 00:03
    Chip,
    What misbehaves first?
    ie what is a good functional test to know that a chip is passing a certain frequency.
    Chip Gracey (Parallax) said...
    Propeller chips are production tested at room temperature to 104MHz (6.5MHz·* 16). So, every part passed a functional test at that frequency. Before the part ever gets hot due to speed, it will just cease to operate properly. However, if you can actively cool it to something like 0 degrees C, you could probably run it pretty reliably at over 128MHz.

  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-12-11 02:37
    The core of each cog breaks down first. The PLL is capable of 160MHz and the hub is half rate clocked.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
  • Bill HenningBill Henning Posts: 6,445
    edited 2006-12-11 07:18
    Umm... I was hoping for some symptoms - ie shifts going wrong, adds coming up with the wrong result, etc.

    The current prop does not have very complex instructions, personally I'd suspect that the cog/hub interaction would be the first to go; but I have no evidence for this, just a gut feeling.
    Paul Baker (Parallax) said...
    The core of each cog breaks down first. The PLL is capable of 160MHz and the hub is half rate clocked.

  • cgraceycgracey Posts: 14,133
    edited 2006-12-11 18:06
    Bill Henning said...

    Umm... I was hoping for some symptoms - ie shifts going wrong, adds coming up with the wrong result, etc.

    Bill,

    The first thing to fail as speed increases is the hub memory access (~112MHz), particularly the hub SRAM read -- this is the critical path in the chip. The next thing to fail is the Z flag (~120MHz), then the C flag (~128 MHz).

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    Chip Gracey
    Parallax, Inc.
  • CJCJ Posts: 470
    edited 2006-12-11 18:23
    so Beau's LED light show would be a good test(lots of hub reads) when testing a speed?

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    Who says you have to have knowledge to use it?

    I've killed a fly with my bare mind.
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