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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Jose on March 22, 2011, 09:56:38 PM
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Interested in 85/90/95/100 mhz. Not sure if oscillator quality matters (goal is to overclock a Cyberstorm MK2) that much but since they're normally cheap I want good quality.
Cheers
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http://www.hy-q.com.au/
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Heh, very cool. A thread with the very questions Ive been wanting to ask. And the same sort of frequencies Id be interested in (Im curious to try overclocking my 40mhz '040 cpu before I upgrade to an '060). Ontop of that the 1st response to the question is from a place thats local to me.
Seems my '040 is destined to be overclocked a little :)
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i had a few problems when ordering oscillators. my first few orders the oscillators did work but had problems after a while. the problem was then found to be the rise & fall time.
i then move from 100PPM to 50PPM,but i now only use 10PPM oscillators built to my specifcation.
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i had a few problems when ordering oscillators. my first few orders the oscillators did work but had problems after a while. the problem was then found to be the rise & fall time.
i then move from 100PPM to 50PPM,but i now only use 10PPM oscillators built to my specifcation.
@op: although ppm specifications are important, especially when overclocking your CPU, I'll try to put it in context for you here. I'm not sure how much you already know about this, so I'll assume no prior knowledge and start at the beginning.
ppm means parts per million. If you purchase an oscillator that has 10MHz output with 100ppm, that means that you can expect to see a frequency drift of 1000Hz over the operating range of the device. For a 100MHz clock, your drift would potentially be 10KHz.
Is this important? Well, for CPU clocking it's generally not important, no. Frequency stability is very important in time critical applications such as reference clocks and stuff like that. It can also be important in some CPU clock situations if a program running on the CPU relies upon the clock to run some time critical tasks. But in your application, that's not the case.
However, it is still important to consider the ppm specification when you overclock the CPU because if you're approaching the clock frequency limit of the system it's possible that a small frequency drift would push it just that bit too far and that would ultimately lead to an unstable system. However, I would suggest that if you're clocking the CPU that close to its operating limit then it's going to be unstable anyway, regardless of a small frequency drift from the oscillator module. So generally it's not something you have to worry about.
If in doubt, purchase a device with a tighter ppm spec. But in any case you certainly don't have to worry about getting them "specially made to your specification", like delshay does.
Rise/Fall time is a separate specification that has nothing to do with the device's ppm. Rise/Fall time refers to the time taken for the device to transition from logic 0 to logic 1. Naturally, a shorter Rise/Fall time is better than a longer one. But, I'd be surprised to learn that a modern oscillator module had such a poor Rise/Fall time that it caused problems with an old 68060 CPU.
AH.
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Thank You App!