iMac G5. High "Memory Controller" temp

[quantumii]

Hi,

A while ago I got myself a G5, which required a reflow of the GPU. I did that, and now the machine works just fine.

I have one concern though. The "Memory Controller" has a very high operating temp. We're talking close to 80c and even more. At least that is the temp reported by Temperature Monitor.

Maybe I should replace the caps? I have a set of new capacitors for the machine, but I have not gotten around to do it yet. The stupid solder is hard to melt. I should probably bring it to the lab at work, where we have professional solder gear.

 

[coius]

is the memory controller in the chipset?

if it is, you might need to re-apply heatsink grease. Also check obstructions in airflow, especially cables. Been a while since I opened an iMac G5 but 80c is what the temp of a lot of things run at in a machine, especially Laptops. Also, the iMac G5 isn't the most well-cooled thing Apple made. first things first, pop off the back and check fans/ obstructions.

 

[quantumii]

Hi,

It's clean inside, and I applied new cooling paste to the chipset cooler already. Yes, I believe Memory Controller is the Apple word for chipset.

Maybe it is supposed to be this hot, but I wonder if it is healthy for it in the long run. The machine seems very little use because of this.

 

[coius]

the cooler a chip runs, the longer it runs, however there are certain windows temp ranges that it is expected to run. If you do a bit of googling, and possibly figure out what the chip number is, you might be able to find the range.

I do know those G5 iMacs run a bit warm, as evident by putting your hand at the vent, you can feel the warm air, and frankly, Apple jam-packed that sucker in tight with little room I am surprised all of them just have issues with Caps.

I would have thought the screens would have had issues from the heat as well. Those G5s run hot, even hotter than the last G4's on the Powerbooks (Man those got warm) and my MacBook Pro seems to get hotter than the G4 systems (Early 2008/2.5Ghz) so they just seem to be getting hotter...

 

[Byrd]

If working fine, and not crashing at all, I wouldn't worry about it. Temp sensors can go awry/faulty and the temp may just be misreported. Even if it is 80deg. C, that's not excessive in today's computer components.

 

[quantumii]

It is running stable, and if I put my finger on the heatsink it does not feel "80 deg c" hot. Maybe the internal die temperature is 80, or maybe as you say, the reporting is actually wrong.

Thanks for the answers

 

[coius]

Keep in mind they may have more than one Sensor for that. Aka one in-chip and one external either on the outside, or slightly off the side on the Heatsink. If it's in the chip, it either could be a faulty sensor, or the die is running at that. Even then, it should be running within limits. If you look at how hot those chips really are at the core, it would astonish you. What matters is how much you can remove at once.

I have been reading a book that says at the actual transistor level, it's 100-1000x hotter from the electricity doing the switching than you actually see on the Die. the Thermistor only picks up radiated heat from the entire chip. Most likely since you aren't experiencing any crashes, it's one of three things:

It's a bad temp sensor

it's reporting wrong, or the application is reading the data/interpretting it wrong

or it could just plain be the operating temp of it.

The only real way to see is to look up and see if there are any documented specs of the operating specifications on the chip. You may have better luck going to whoever made the chip (whether it's TI, Agere (that's what's in my G4) or whatnot. That's about as good of a guess you are going to get.

Frankly, I wouldn't get worried unless the machine crashes, or smokes itself. in any event, replacing the heatsink grease, making sure air flows well and whatnot is the best you can do. if it is a faulty chip, there's nothing you can do until it goes out and decide whether to replace the board or not.

Just enjoy the iMac as it is, I have not to this date heard anything about the chipsets being bad on those. Only the Capacitors.

I have a question, does anyone know if the G5 had an internal memory controller every? Or was that their POWER4 Chips that had that (The POWER4 is what the G5 was based off of, right?)

 

[coius]

ick... they used an external Memory controller... Bummer, would have been better (but probably would have increased the thermal characteristics of it) if they put it on-chip rather than going through the rather-slow bus they had..

Also seems according to wikipedia that there was significant overhead which crippled transactions on the bus, including memory performance..

 

[quantumii]

Yeah, I guess I will just leave it as it is now. There is very little airflow over that particular heatsink (It is under the Apple logo under the screen). I guess this is an example of an odd design.

 

[mcdermd]

I have an iMac G5 iSight here who's memory controller was sitting at over 60*C at idle. I don't think you're too far off the mark.

Incidentally, I have repaired a lot of these iSights that have had bad capacitors on the back side of the logic board, behind the memory controller's heatsink. They all have been of the "bad cap" types and are in a high heat area which, I'm sure, is why they fail regularly. To my knowledge, Apple never offered any sort of warranty extension for these models.

 

[khmann]

I didn't catch whether you were talking about iSight or not (iSights in my experience have far more graphics troubles), but anyway at least the ALS model has a chip on the back of the board with a heatsink. the thermal compound there might need replacement.

 

[techknight]

I had to reflow that vary same IC in mine. it runs hot with the cover off as well.

it doesnt run AS hot with the cover on, and there IS airflow across the chip. When the black/aluminum sticker film is applied across the IC, the fan off to the left pulls air through the IC, but it could be better.