Classic Mac Hardware (Troubleshooting, Upgrading, & Modifying) > Mac CPU Upgrades

Why it IS important to use the right heat sink ... (Sonnet upgrade)

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Bolkonskij:
After I got my copper heatsink I replaced it with the (thin) aluminum one that came with my MDD when I got it. Well, well ... after removing the heatsink I discovered THIS:

http://images.macintosh.garden/2021/09/15/kebab-board.jpg

Apparently I drove it a bit too hard encoding all those Quicktime videos for Cornica. Today on the menu: roasted Sonnet upgrades :-(

Surprisingly, it still worked flawlessly! Went to carefully wipe the "smoke" off with isopropyl alcohol. Didn't come off 100%, but looking way better than in the initially taken photo above. Then repasted the CPUs with some Arctic Silver MX-4. After that I put the new copper heatsink on - which will hopefully avoid something like this in the future. Connected it to the Cinema Display and booted it - a chime. The welcome  screen appears. I'm in OS9. Whew! I'm sure ya'll can relate to the emotional rollercoaster ... :-)

Lesson learned: Don't save money on a quality heatsink. Especially with G4 / G5s ...

FBz:
Sheesh!

Man, that’s a whole lotta hotta.


What’s with the aluminum foil looking appearance on the two chips? Is that Arctic Silver MX-4? Looks more like a metal foil covering. And the blackened areas look like extreme heat transference from an overly hot heatsink positioned just above them. Just how torqued-down (tight) was that heatsink that you removed?

Might also want to check that all fans are definitely working properly. How “full” is that case with HDs? I’d pull any remaining conventional spinning drives and only use SSDs on the back bus. (Nothing possibly obstructing air flow on the front bus from optimum airflow to the large fan to cool the CPU / heatsink.) AND quite possibly, say a permanent good-bye (remove /replace) any old Apple ADC powered Cinema Displays. Increased demand and thus an interior heat increase overall from a hotter PSU under that ADC load.

Looks as if you’ve already closely approximated the “China Syndrome” …so may be time to lighten the internal load overall and optimize cooling to possibly preserve or extend the life of that Sonnet. AND remove all unnecessary expansion cards, not directly related to your primary tasking. What’s that old equestrian adage? “Rode hard and put away wet”?

OR:
“Come to kindly terms with your ass, for it bears you.” -John Muir

Very loosely related errata, and just for fun…
https://alumni.berkeley.edu/california-magazine/fall-2017-bugged/zen-and-art-bug-repair
(Interesting Steve Jobs passage there too.) “…so it would never go out of fashion”.

IIO:
i must have something like that in my atari. one day all of a sudden a strange smell filled the room so that i had to open the window.

Bolkonskij:
The MDD has no HDDs for less heat / maximum air flow, just a single SSD inside. It gets regular cleaning with compressed air. Fans do work. heatsink was screwed tightly (I onced toasted a cpu with that, believe me, I make sure now). Really, the issue here was probably using the machine on a hotter day in conjunction with that (thin) aluminum heatsink. Bear in mind, this is an overclocked dual 1.67 Ghz Sonnet upgrade (the one from Knezzen) and it runs pretty stable, but obviously it needs a better cooling than the stock heatsink provides.

Speaking of stock heatsinks, can anyone confirm that dual 1.25 Ghz MDDs were actually equipped with the thin aluminum heatsinks? I thought Apple had already switched to the thick aluminum ones due to heat issues?

peeperpc:

--- Quote from: Bolkonskij on September 15, 2021, 11:34:35 PM ---Speaking of stock heatsinks, can anyone confirm that dual 1.25 Ghz MDDs were actually equipped with the thin aluminum heatsinks? I thought Apple had already switched to the thick aluminum ones due to heat issues?

--- End quote ---

The thin aluminium one is the newer one. It dissipates heat better than the thick one. I have tried both.

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