Notes on re-pasting the Mac Mini G4 CPU

[karl]

My G4 mini is my go-to OS 9 machine, and I decided to replace the thermal paste since the fan has been quite loud, even when idle, ever since I bought it on eBay a couple years ago. I don’t have any scientific measurements for before/after, and I don’t think the fan is spinning any slower/quieter after the new thermal paste, but subjectively I now feel more heat escaping the machine through the rear exhaust, so I think the cooling system is at least running more efficiently. Here are my observations:

• I was a little confused about whether the G4 mini used thermal paste or a thermal pad on the CPU. The GPU (on the underside of the logic board) uses a thermal pad to conduct heat to the bottom of the mini’s case. The CPU used what I would call a black, thermal grease. It came off with isopropanol, but it was very dry and crumbly, probably well past its prime.
• I was expecting the mini to be quite dusty inside, but it had hardly any significant dust at all, so I didn’t have any easy thermal gains blowing that out.
• I’d never re-pasted a bare die CPU before, always been spoiled with modern Intel/AMD IHS. It turned out pretty easy, popping the heat sink off was the slightly tough part (gotta squeeze the plastic pins back up through the logic board bottom).
• There is an extremely thin plastic shroud that directs the air out of the heat sink. In mine, the shroud’s glue had dried up, so it was partly detached from the plastic assembly it originally stuck to. I just used tape to put it back in place.
• I did not replace the GPU thermal pad because it looked like it was still in perfect condition, and I figured any random thermal pad I bought on Amazon might be a quality downgrade. Eyeballing it, the pad looked to be about 0.5mm thick, but tough to tell.
• I did not overclock my mini (it’s a 1.33GHz with a 1.25 label on the case), largely because I had already reapplied the heat sink before realizing, since my model is 1.33GHz, I would need to add one of the jumper resistors to a site underneath the heat sink in order to OC to a known speed (I couldn’t find a reference to what speeds are possible when configuring the other 4 jumpers while leaving the 5th unpopulated).

All in all, the mini’s power management under OS 9 still means high fan RPMs while idle, and I probably could have been fine just leaving the existing thermal compound in place, but at least now I know it should be good for another 17 years or so.

 

[trag]

All in all, the mini’s power management under OS 9 still means high fan RPMs while idle, and I probably could have been fine just leaving the existing thermal compound in place, but at least now I know it should be good for another 17 years or so.

Is the fan management not proper under OS9? Otherwise, how are you liking 9 on the Mini?

I have a few G4 Minis and I vastly prefer OS9 to OSX, but there are always compromises with the mods needed to run OS9 on unsupported machines...

 

[karl]

Is the fan management not proper under OS9? Otherwise, how are you liking 9 on the Mini?

I have a few G4 Minis and I vastly prefer OS9 to OSX, but there are always compromises with the mods needed to run OS9 on unsupported machines...

I think OS X is able to put the CPU in a lower-power state than OS 9 can; in my experience running OS X on a G4 mini back in the late 2000s, the fan was silent when idle or doing basic tasks. Besides that and the lack of a sleep mode or usable internal speaker, OS 9 on the mini is great.

 

[PPC_505]

I just repasted mine this week (before I saw this thread) as part of my OC to 1.58Ghz. The exhaust does feel warmer now, but I've noticed the improvement in performance. The fans will run at what seems like max if I'm multitasking while uploading to the Garden in OS X (simultaneous uploading through Interweb, making more disk images, and looking through PDFs, etc). Doesn't bother me much though.

 

[retr01]

Hi @karl!

Your Mac Mini G4 is the model A1103, correct? How well does it serve as the middle between modern and older Macs as an OS 9 machine?

 

[tkn]

I've got a G4 Mini, bought off eBay a few months back. It came with 10.5 Leopard pre-installed, which was fine, but I had intended to go back to 9.22, and wanted the fastest possible machine that could natively run it. Hence, the Mini. I ended up with an A1103 10,2 1.33 "Silent Upgrade" model. The first A1103s, the 10,1 used the same 7557 chip, but clocked at 1.25 and 1.4 and lacked Altivec support. The 10,2 models were unannounced and reportedly some people who ordered the slower models received the new ones.

Apple went as frugally as possible with the mainboard, since they used a simple resistor matrix (I don't know what to call it, I'm not IEEE) that has positions for all four clock speeds so they didn't have to make new boards. Efficient. The following illustration shows some of the positions. I'm not sure where the 1.33GHz model is, but this gets you somewhere

I saw this on a very recent video uploaded by the House of Moth.

• (2) Overclocking a mac mini G4 - YouTube

I haven't soldered anything since I was a kid back in the 70's, so I doubt I could do this anytime soon, but I sure would like to. What I wonder is if my 1.33 can reach 1.58. Of course, the concept of chip binning has been around for a LOOOOONG time, so I have my doubts. It's a lottery.

Hi @karl!

Your Mac Mini G4 is the model A1103, correct? How well does it serve as the middle between modern and older Macs as an OS 9 machine?

It works fantastic with Mac OS 9, except it's not capable of booting 9 without some modifications. I use RossDarker's Mac Mini OS 9 CD v9 restore ISO from MacOS9Lives (http://macos9lives.com/smforum/index.php/topic,4365.0.html) which has all of the instructions you need. There are some minor caveats to note.

* One is the audio is weird in that it doesn't work for the integrated speaker, but it does do near line-level output from the headphone jack, so a pair of amplified speakers with their own volume controls will be necessary. Or just a little amp that you can plugs speakers and a pair of headphones into.
* Two is is you are using a DVI to HDMI cable to your monitor. It likely will NOT give you a usable resolution when you first boot the CD-R. If, however, you are familiar with MacOS 9, you can change it. Open the CD in Finder, open System Folder > Control Panels, and open the Monitors CDEV. Its the older version so the top, right button is for opening the Resolution dialog. 1280x1024 works best.

Once you have it installed, however, the system on the CD will offer you better resolution options, but you'll want to upgrade the video drivers. It's a manual affair, though, and there are a few different, partial collections available. I can't do a write-up right this second, but I am working on a small package that includes everything needed to get the G4 Mini outputting 1920x1080. I accidentally lost the work, however, when one of my PATA drives failed. whee. It's not a load of work, but I'll need to rewrite the README again and redo all the screen pics (since I can't do screen grabs booted from the CD... unless anyone has a suggestion), but I will get to it soon.

 

[tkn]

I just repasted mine this week (before I saw this thread) as part of my OC to 1.58Ghz. The exhaust does feel warmer now, but I've noticed the improvement in performance. The fans will run at what seems like max if I'm multitasking while uploading to the Garden in OS X (simultaneous uploading through Interweb, making more disk images, and looking through PDFs, etc). Doesn't bother me much though.

What was the factory speed for that machine? I've got a 1.33 model, which is a real stretch, considering these chips were binned and wafer reliability was way worse back then. Thanks!

 

[PPC_505]

What was the factory speed for that machine? I've got a 1.33 model, which is a real stretch, considering these chips were binned and wafer reliability was way worse back then. Thanks!

Sorry for the slow response. Mine was a 1.42 originally.