Overclocking Question

chemistry_geek

chemistry_geek

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Slashdot has an article here:

http://slashdot.org/articles/02/01/17/1823233.shtml

about overclocking the hell out of a Pentium 4 to 3.5GHz using liquid nitrogen.

Now, being a graduate student in chemistry, I have access to LOTS of liquid nitrogen and a PowerPC G3 that normally runs at 500MHz. I'm wondering if I could do something similar with my IBM 500MHz G3 that the guys over in Finland did. I've overclocked it before to 600 Mhz with absolutely no functionality in Mac OS X (did not startup), Mac OS 9 ran very fast for about 20 minutes then every program crashed. But reducing the overclock to 550Mhz, it ran in Mac OS 9 for 30 minutes before memory errors started cropping up and I got a kernel panick in Mac OS X during startup. Just for your information, my IBM G3 500MHz is a replacement processor of the original Motorola G3 400MHz. I ordered it from http://www.allmac.com and since they sent me the WRONG heat sink, the same one for the 400MHz G3, I placed a fan on my original heat sink to keep the IBM 500MHz G3 cool. So my new IBM G3 runs cooler than my original Motorola 400MHz G3 and I was never concerned about overclocking it 100MHz above factory specs. Any ideas if liquid nitrogen might work with a really overclocked G3? What I'm asking is, will there be serious timing errors within the processor that will prevent a successful run at 78 Kelvin (-319.27 degrees Fahrenheit = -195.15 degrees Celsius)? I think this would be so cool to have a G3 overclocked to something like 800MHz (the max allowed with the logic board I have - involves moving some jumper switches).
 
Just tried to overclock the processor again to 550MHz in Mac OS X, with the case open since the CPU runs cooler with fresh cool air blowing in it. It successfully booted into OS X and ran for 10 minutes, then I saw a pale blue screen for about 5 seconds with the spinning beachball, and then back to the login screen. I shut down the computer immediately, reset the CPU clock rate to 500MHz, no problems. It seems that this thing refuses to be over clocked, even with a fan cooling the CPU. The only thing I can think of that is causing the problem is that the 1MB of cache memory on the processor is heating up too much. I might need a heat sink for that too. I'm spending way to much time on this, can't do this anymore.
 
You know, I still have the original Motorola 400MHz G3 CPU daughter card that still works fine. When I lost the logic board from the static electricity last September, the university PC repair said that unless they had special equipment, which they did not, they could not determine if the CPU or the logic board was fried. But they did say that the CPU almost never fails in an Apple...unless it was overclocked by some overzealous idiot without proper precautions. I may try the liquid N2 with the 400MHz G3, but not the new 500MHz G3. I'm brave, but not stupid. I would hope that 78K (-319.27 degrees Fahrenheit = -195.15 degrees Celsius) would allow any CPU to be overclocked to a reasonable speed. If I do this, I will take photos with the department's digital camera and upload them for all to see.
 
Electronics is a bit more complicated.

Your computer also use non-volatile memory (Flash) and other parts (clock...) that must operate within a given voltage, temperature and speed range. If you change it too much it will simply not operate any more.

In addition if the temprature change is too fast, the package of your chip or the chip itself may brake !

So, if you can run a pentium or a PPC at very high speed a low temp, this doesn't meana Mac (or a PC) using standard components can operate at very low temperature.
 
I once tried to overclock in 2 settings...420 MHz and 120 MHz bus on my B/W G3 ran pretty good except the ethernet port got disabled. Internet doesn't work....and tried 94.5 MHz bus at 472 MHz same thing....I think that ethernet port hates bus speed changes....strange....but do u any of u know how to fix that? Thanks
p.s. 120 MHz bus at 420 MHz was fast!
I'm at default 100 MHz bus at 450 MHz overclocked from 400.
 
I don't know how to solve your ethernet problem while overclocked. My overclocking knowledge is very limited to the articles I've read around the net. And believe me, I make sure that the processor stays cool, or doesn't heat up too quickly. I don't have another $300.00 to blow on a new G3 processor daughter card. I have "ThermoInDock" running all the time whenever I get into the mood to overclock. Things do warm up a bit though.
 
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