Hi-
The power that feeds the CPU through the logic board in the Sawtooth is 1.8v-2.1 (the later for L2 cache).
The I/O bus adds 3.3v to the mix.
The 7400 series proocessors in the Sawtooth required the higher voltage.
This voltage is too high for use with 7447A processors
The move to 7447A processors in later Powerbook models was due to reduced voltage needs, and the resulting reduced heat production.
The core voltage for the 7447A at 1GHz is 1.1v, with 1.3v for 1.33GHz and 1.5v used as processor speed reaches 1.42 GHz.
It appears that the 1.5v setting doesn't allow enough power through to run stable at 1.8GHz, but the 1.55v setting does.
It seems to me that you have determined the working settings for the processor and that Sawtooth.
Since it is stable, I would use it and not worry.
Even the advice of gigadesigns mirrors what you have done:
Here's the message from Tim @ gigadesigns.
"Perhaps the voltage needs a little fine tuning. Please find your current voltage jumper setting on the list below, and try a setting which is one setting higher than your current setting. If you experience no improvement, please try a setting which is one setting lower than your original setting. If you are still experiencing a problem, try a setting that is two settings higher that your original setting. If the problem persists, please contact me by telephone at the number below, or via email for further troubleshooting assistance.
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One other item, regarding board voltage, is that since you have an ATX PSU, you have a more robust power source than the OEM.
When the CPU calls for voltage, it gets it.
It is possible that the voltage settings may need to be higher with a weaker PSU.
Then again, a weaker PSU was/is a common problem with heavily upgraded machines, as the OEM can't supply the needed voltage under load.
