Time for some new paste. It seems to be working well this time around, as none seemed to get pushed off either CPU die, and it can hold 48.5c steady idle on CPU A when on “highest”. The Power Mac G5 feels snappy again! And these heatsinks are pretty decent.
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Why I repasted the CPUs

The Power Mac G5 was starting to overheat. I knew the room temps were fine, airflow was fine, and I’m pretty sure I put new thermal paste on the CPUs sometime within the last year. What gives? As it turns out, it can be tricky getting just the right amount on here.
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Before

CPU A

CPU B

The thermal paste wasn’t old, but somehow it was being pushed off of the CPU die despite being careful as to the amount I put, and being careful to reassemble it properly. It gets frustrating to put new thermal paste every year only to find out this is the ultimate result.
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Putting the new MX4 on

Like before, I was careful as to how much I put on the die. This time around, rather than letting the squeeze-pressure of the heatsink to spread the paste when inserting the CPU card, I spread the paste using a piece of cardboard. I think this was the right amount, judging by the post-assembly temperatures and how steadily they’ve been hanging.
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It doesn’t take much to get into the Power Mac G5’s CPU card, it takes less than 7 minutes to get to the point of scraping off the old thermal paste. So it’s not such a big deal doing this all over again.
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After

Now, it runs a-ok, cool even, on the “highest” power option in “energy saver”, no more randomly going into sleep mode, and these massive heatsinks actually do pretty well to cool the first-gen G5 when paired with Arctic MX-4. Now, the CPUs breathe a little easier.
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In room temperature, when idling, the Dual 2.0 G5 dips down as low as 109F for CPU A and 95F for CPU B. I also noticed it’s able to achieve slightly higher Power Fractal scores, after giving it new thermal paste. Previously, it topped out at 13.8 GigaFlops, now it can consistently do 15.

After New MX-4

Before new Paste

This means this Power Mac G5 can properly go toe to toe with a 2006 iMac when properly maintained. Previously, I thought 13.8 GigaFlops was simply the best a Dual 2.0 G5 from 2003 could do, but it turns out there was a little more room for oomph. Both tests were conducted with CPU setting on “highest” in energy saver.
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Now, it can steadily stream 720p video again while dropping few to no frames. The CPU temps top out at 66.6c in a warmer room, surprisingly. The GPU still does alot of heavy lifting, of course.