Did you try just a K6-2 fan, or a K6-2 heat sink and fan?

It would take some sheet or metal bar work, but you might consider trying to mount some of the modern heat pipe equipped heat sinks on the thing. Something like the Scythe Samurai Rev. B, or the ThermalTake XP-90C (not sure you can still find that one, try Walmart.com). Or the OCZ Tempest.

The tricky part would be getting from the mounting screw points built into your mac to something that will mate with the mounting points on the heat sink. This can probably be done with properly size metal blocks, if you're willing to drill and tap some screw holes.

So, figure out what size metal block would be needed as adapters, go to your friendly local metal shop and buy the proper sized pieces (have them cut them to size), take them home and drill holes for the screws to the Mac case, and other holes for the heat sink screws to mount to. Then tap (make threads in) the holes for the heat sink screws to the proper size threading.

Unfortunately, you could easily spend $100 on the heat sink, metal, drill bits, taps and a tap handle, if you don't already have the tools and make a few false starts. The nice PC heat sinks often cost in the neighborhood of $50.

At that price point, you're probably better off just buying a faster CPU card, unless you really want to experiment with extreme cooling.

It sounds like an interesting experiment to me, and I bought some heat sinks to try in the dual 1.25 GHz MDD, but I have not made time to design and build the mounting adapter and do the tests.

The trick to picking a PC heat sink for the dual G4, is to get one with a wide enough base (~50mm+ IIRC) to cover both CPU dies.

Did you try just a K6-2 fan, or a K6-2 heat sink and fan?

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Only the fan screwed to the original B&W rev.2 Heatsink.

If I get a heatpiped one, I'm afraid the real problem would be closing the case :-/ . I have seen some of these and they are really huge. On later G4s that might not be a problem because the processor position changes to a larger area, but in my case, it's still a ZIF (it gets really tight with the B&W/Yikes! case closed). I thought about adding a peltier cell, but there are risks of condensation. Other possible solutions?

PS.: Is it possible to remove the zip drive and the support below by only removing their screws?

Could PSU be the source of the problems? the computer freezes at 43°C when running at 500mhz.

Here's an idea. Settle in at 450mhz and stop pushing it to 500 before you fry it. Bumping a 400mhz chip to 500mhz is a 25% overclock, which is really pushing it with air cooling. You can try to find a copper heat sink that will fit it because copper is more thermally efficient than aluminum and a fan that provides greater airflow, but I think you're really pushing this chip far beyond it's limits already.

Here's an idea. Settle in at 450mhz and stop pushing it to 500 before you fry it. Bumping a 400mhz chip to 500mhz is a 25% overclock, which is really pushing it with air cooling. You can try to find a copper heat sink that will fit it because copper is more thermally efficient than aluminum and a fan that provides greater airflow, but I think you're really pushing this chip far beyond it's limits already.

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But it never overheats. it freezes at 43°C only, while at 450 it would go beyond 60°C and stay operational. I will look for a copper heatsink, thanks.

What is the maximum voltage for that CPU?

one of the problems you could be having, is interfearance inside the CPU itself. If you get it too fast, you may be causing electricity to cause interfearance from the heat INSIDE the die, and not on the surface. Despite being able to get rid of heat on the surface, the inside of the die may actually be much hotter than the ceramic/metal on the cop of the CPU. It also could be arcing electricy causing interfearance and bad data inside the chip. So i would say, either buy a faster CPU, or drop the speed. 50Mhz isn't going to make too much difference, especially with OS X being more reliant on the GPU than the cpu. I would drop the CPU to 450, then get a better Graphics card. It will pay off more in the end, and see more responsiveness from that.

Also, if you want better speed, use 10.3.9, and stay away from 10.2, and 10.4 . those are the worst offending systems on a slower system like yours. 10.3.9 is optimaized best for systems under 700Mhz, and it will prevent uneeded servise (like Dashboar) from loading, and reduce processing power needed to run the kernel. It would be the perfect system for that.

I use 10.3.9 on my lombard, as it's faster than 10.2, and doesn't have the bulk that 10.4 puts on it. So it's not like I am getting the features I want, but it also doesn't have the bog down and bloat coding of 10.2

I personally think that 10.3 is THE BEST for sub-1Ghz systems. Even 10.4 seemed slow on my 1.2Ghz iBook G4.

Get a faster or dual powermac G4 before spending any more on that B&W/Yikes!. it's not worth trying to get more power from a system that old. Either that, or stick with 10.3

BTW, if you upgrade the GPU, make sure you get one that can utilize the 66Mhz Slot, or if you can, get one that is 64-bit (yeah, i know, it's hard to) but that will give you the best through-put and system speed increase that you will notice a HUGE Differnce. CPU speed is overrated under OS X.

Also, if you want better speed, use 10.3.9, and stay away from 10.2, and 10.4

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I only have Mac OS 9.2.2 and 8.6 installed. It's just what I need for now.

And when I jumped from 400 to 450mhz, I saw a huge difference indeed. I imagined if I took one step forward I would see the same difference. At least, the Quake loop I leave for stability testing showed a noticeable difference on both steps.

For the Video card I have a Radeon 7000 64mb. It's performing very well for 2D/3D. I just wanted to take full advantage of my current hardware without upgrading it. If I took a faster processor, it would have to be from 3rd party manufacturers, which I don't like very much and could lead me to incompatibility problems.

What is the maximum voltage for that CPU?

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That would be 2.7v, which I already tried. From that point the temperature starts to rise already. I had over 63°C running at 450mhz idle.

If I took a faster processor, it would have to be from 3rd party manufacturers, which I don't like very much and could lead me to incompatibility problems.

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What's wrong with Sonnet?

I don't know. Maybe some game would conflict with it's drivers, which will also slow the whole system down. I heard that it would also restric mac os versions I can use. I need full support for Mac os 8.6. And its minimum is a powerpc 7410. For some older apps I need to throttle it down on the fly with G3 throttle, which only recognizes the PPC 7400.

Sonnet works (for instance, the 500 MHz Encore) from 8.1 to 10.4 with XPostFacto.

Sonnet works (for instance, the 500 MHz Encore) from 8.1 to 10.4 with XPostFacto.

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But this is for the beige, right?

i have a sonnet 700 mhz running 10.4. The only problem i have is no dvd rom in the b&w and it will not boot off of fire wire. lucky for me i got a set os 10.4 cd's from apple. this has helped with several project machines. I also have my 5 machine family pack in dvd. i dont want to be accused of piracy!

I may purchase another identical zif module than mine to see if it performs better, lets hope yes. Only this model guarantee the compatibility I need.

My B/W G3 has a Sonnet G4/400 in it an so far the only thing that needed to be installed was a firmware patch to allow G4 processor upgrades. Other than that no drivers were neccessary.

Sonnet works (for instance, the 500 MHz Encore) from 8.1 to 10.4 with XPostFacto.

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But this is for the beige, right?

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Not just that. This is for the Power Macintosh G3 "Beige" to the Sawtooth.