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netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
Hello community,
today I repasted my iMac G5 iSight in hope of getting it to cool down a little bit but the temperature readings still seem to be out of what is acceptable. Especially the memory controller is noticeably high (usually goes up to 90 °C / 194 °F no matter what I do. I attached a screenshot of my temperature readings when at full CPU load (by running a looping terminal command). Now I wouldn't be bothered if it weren't for the 2 memory controller readings. What else could I try in order to get the temperatures down and what are these 2 memory controllers (where are they on the logic board) ? Any recommendations are highly appreciated. Many thanks!
 

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Jubadub

macrumors 6502
Nov 1, 2017
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90°C is indeed suspiciously hot, although the CPU temperature and fan speed displayed in your screenshot seem to be within what's acceptable. Well, actually, I was wondering if your fan is spinning enough, because at 72°C, I think it should be spinning quicker than 1623rpm...

What is the CPU fan rpm when temperatures reach 90°C?

Also, what thermal paste did you use? Could you describe for us, in detail, how you applied it, so we can have a better idea?
 

netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
90°C is indeed suspiciously hot, although the CPU temperature and fan speed displayed in your screenshot seem to be within what's acceptable. Well, actually, I was wondering if your fan is spinning enough, because at 72°C, I think it should be spinning quicker than 1623rpm...

What is the CPU fan rpm when temperatures reach 90°C?

Also, what thermal paste did you use? Could you describe for us, in detail, how you applied it, so we can have a better idea?

Thanks for replying. The fan is indeed not spinning any faster than about 1600 or 1700 rpm but as you've pointed out the CPU stays relatively cool. Now I haven't really used the machine much today I only browsed the web and that's about it although the iMac reached 100% load when I use TenFourFox. When the memory controller reaches about 90 degrees the fans really don't care and stay the same. I've used MX-4 thermal compound which I used in my PowerBooks G4 before and it is a really good paste from what I can tell (applied it via the dot method and then spreading it with a card). Where are these memory controllers located by the way?
 

netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
So I took the iMac apart again and repasted the memory controller as well (the pin fin heat sink at the front of the logic board covers the memory controller, it has to be detached with tweezers in order to get to the controller) but the temperature isn't really any different. I mean it does not get to 90 °C that quickly but eventually it'll be around 85°C again. The CPU and GPU don't get that warm. Is this a thermal design flaw or why does the memory controller get so damn hot? It doesn't even matter what I do on the computer. Does anyone in here have the same machine as I do and could share his/her experience regarding memory controller temperature. What do you guys think 85 °C isn't really that safe anymore when being constant, right? Thanks!
 

Jubadub

macrumors 6502
Nov 1, 2017
342
425
A server-class processor like the G5, to my knowledge, should endure higher constant temperatures than other kinds of processors. I believe Raptor computing said such temperatures are "normal" and "acceptable" for their Talos II line, for example. So I'd expect more or less the same to apply here.

Still, it's reasonable to want to bring that down, especially considering all the other components in the board, and the board itself.

Random suggestion, but have you thought about finding a bigger heatsink? And it'd be good to find a way to speed those "slow" fans up, too, perhaps... Not sure how/if that can be done via software.
 

sparty411

macrumors 6502a
Nov 13, 2018
552
499
So I took the iMac apart again and repasted the memory controller as well (the pin fin heat sink at the front of the logic board covers the memory controller, it has to be detached with tweezers in order to get to the controller) but the temperature isn't really any different. I mean it does not get to 90 °C that quickly but eventually it'll be around 85°C again. The CPU and GPU don't get that warm. Is this a thermal design flaw or why does the memory controller get so damn hot? It doesn't even matter what I do on the computer. Does anyone in here have the same machine as I do and could share his/her experience regarding memory controller temperature. What do you guys think 85 °C isn't really that safe anymore when being constant, right? Thanks!
The iMacs have garbage airflow, to my knowledge. I would consider those temps to be within normal operating spec.
 
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1042686

Cancelled
Sep 3, 2016
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Do you think the ram could be starting to fail or maybe it’s the wrong clockspeed & is pushing the memory controller harder causing the high temps? Does the ram itself get hot?

Got some other ram to swap in & test temps?

Also, I wonder if there is space for a small thin fan to be mounted over the MC heatsink to help Move air?
 
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netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
Do you think the ram could be starting to fail or maybe it’s the wrong clockspeed & is pushing the memory controller harder causing the high temps? Does the ram itself get hot?

Got some other ram to swap in & test temps?

Also, I wonder if there is space for a small thin fan to be mounted over the MC heatsink to help Move air?

These are actually quite interesting points you made. The RAM appears to be fine and isn't warm at all but I'll have to look around the house to see if I got another suitable RAM stick lying around. The 2 GB stick I'm using is from a 10 pack that I ordered on Ebay a couple of months ago (https://www.ebay.de/itm/10PCS-Micro...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649). I've put 8 sticks from that pack in my PowerMac G5 Late 05 and they work like a charm in it so I don't know if actually the RAM module itself is at fault. The iMac G5 at least seems to be handling it correctly as well but maybe I should run AHT to verify that?

I have some spare fans from other Mac computers such as the 12" PowerBook, the original MacBook Air and older pre unibody plastic MacBooks. These are more or less tiny but the question is how can I connect them to the power supply to power them (I never attempted such hacks).
 

jmilan0302

macrumors regular
Feb 8, 2019
158
47
The iMacs have garbage airflow, to my knowledge. I would consider those temps to be within normal operating spec.
Nah, the G5 iMacs actually has pretty decent airflow. Especially the iSight ones, the CPU fan is in the middle, where the rear vent is, so the plastic iMacs had some of the best airflow of all iMacs.
 

1042686

Cancelled
Sep 3, 2016
1,575
2,323
These are actually quite interesting points you made. The RAM appears to be fine and isn't warm at all but I'll have to look around the house to see if I got another suitable RAM stick lying around. The 2 GB stick I'm using is from a 10 pack that I ordered on Ebay a couple of months ago (https://www.ebay.de/itm/10PCS-Micro...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649). I've put 8 sticks from that pack in my PowerMac G5 Late 05 and they work like a charm in it so I don't know if actually the RAM module itself is at fault. The iMac G5 at least seems to be handling it correctly as well but maybe I should run AHT to verify that?

I have some spare fans from other Mac computers such as the 12" PowerBook, the original MacBook Air and older pre unibody plastic MacBooks. These are more or less tiny but the question is how can I connect them to the power supply to power them (I never attempted such hacks).

I’m unfamiliar with the imac G5 as I don’t own one but if the heatsink has any sort of fin, you might be able to screw the fan right onto them with the four mounting screws grabbing inbetween the fins. I’ve mounted a few extra fans into powermacg4 heatsinks that way. I’ve also used zip ties with great success for those times where I can either anchor around the heatsink (no fins) or where there was convenient holes to fish through in the circuit board.

I did install an extra fan into the upper right hand corner of my 24” white intel iMac for extra circulation. I ran power from the hard drive, so my intuition says with the right sized fan running power from your hdd using a Y, you probably could get one in there, obviously being flexible in how you mount it.

I had the luxury of running SMCfan control on that box to ramp up fans when I wanted but IIRC that is intel specific (could be wrong there) so am unsure what app to use in a ppc OSX box.
 
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netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
I’m unfamiliar with the imac G5 as I don’t own one but if the heatsink has any sort of fin, you might be able to screw the fan right onto them with the four mounting screws grabbing inbetween the fins. I’ve mounted a few extra fans into powermacg4 heatsinks that way. I’ve also used zip ties with great success for those times where I can either anchor around the heatsink (no fins) or where there was convenient holes to fish through in the circuit board.

I did install an extra fan into the upper right hand corner of my 24” white intel iMac for extra circulation. I ran power from the hard drive, so my intuition says with the right sized fan running power from your hdd using a Y, you probably could get one in there, obviously being flexible in how you mount it.

I had the luxury of running SMCfan control on that box to ramp up fans when I wanted but IIRC that is intel specific (could be wrong there) so am unsure what app to use in a ppc OSX box.

So I tried a different RAM module (same memory size but different brand) but the heat situation remains unchanged. In my drawer I had two fans sitting that could be candidates for a cooling mod since they fit physically. I'd simply stick them to the logic board with a heat resistent double adhesive tape. Using a cable to split the SATA power supply is actually a great idea but how would I convert the connectors of the fans to make them plug with SATA? Are there any converters / adapters that do that? Also I don't know if the position of the additional fan is ideal and how I could control the additional fan from the OS. It seems that doing such mod isn't too straight forward unfortunately but if anyone could point me in the right direction I'd love to try it out.
 

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jmilan0302

macrumors regular
Feb 8, 2019
158
47
So I tried a different RAM module (same memory size but different brand) but the heat situation remains unchanged. In my drawer I had two fans sitting that could be candidates for a cooling mod since they fit physically. I'd simply stick them to the logic board with a heat resistent double adhesive tape. Using a cable to split the SATA power supply is actually a great idea but how would I convert the connectors of the fans to make them plug with SATA? Are there any converters / adapters that do that? Also I don't know if the position of the additional fan is ideal and how I could control the additional fan from the OS. It seems that doing such mod isn't too straight forward unfortunately but if anyone could point me in the right direction I'd love to try it out.
Use the black fan, just make sure the side which it blows air out of is pointing at the heatsink. Also get it as close as possible to the heatsink. To power it, you will have to cut off the connector and solder on wires to the right pins, and then connect that to 5v.
 

netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
Sorry it has been some time. My cooling mod is finally finished and now I can enjoy a much cooler iMac G5 :) I ended up buying a bunch of 3pin Molex (12V) fans which I attached via double adhesive tape near the hot zones. 2 are near the Northbride, one on the SSD and one near the optical drive. To power said fans, I split the SATA power connection by using a Y-Cable and a cheap SATA power to 8x3pin Molex adapter (so no soldering skills required). It works great and the Northbride temperature dropped by about 15°C. SSD and optical drive caddy were about 60 degrees before which is way to hot IMO. SSD dropped by 5-10°C and the optical drive caddy about 3-4°C (I mounted a very small fan there). The additional power consumption is about 3 watts.
 

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netsrot39

macrumors 6502
Original poster
Feb 7, 2018
357
487
Austria
Very cool. How much did this cost?

The two fans near the northbridge were rather pricey (about 15$ each – Amazon). The other 2 ones were approximately 10$ in total (AliExpress). The SATA to Molex Adapter is very cheap like 2$. The SATA splitter as well, it is like 1$. So I'd say I spent about 40$, of course that wouldn't be worth it for an old machine for the average joe but I'm a hobbyist so I don't mind putting money into older machines.
 
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