Calling All MDD Owners / CPU Temp ?s

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TheUltimateMacUser's picture
Joined: Jan 28 2004
Posts: 615

I've been doing a bit of research into this, and based on that research, i think my MDD G4 is running a bit hot. Im currently seeing a CPU temp around 113 deg F (45 deg C), and that's with my fans running full tilt. I'll also point out that this is in a room with an ambient temp of around 65 - 68 deg F. The inside of my computer is dust free, and most of the PCI slots are unused; although i do have CD/DVD drives in both drive bays. Some google searching turned up a few suggestions to 'enable nap mode', and reports of that drastically lowering the average CPU temp. I'm also thinking of adding a PCI slot fan to suck warm air out of the case.

I have a few questions i'd like to ply on the AF community:

- Those of you with MDD G4s (esp. those of you w/ dual 1.25 machines), how hot is your CPU running?
- Are the above listed temps abnormally high?
- If so... would either of the above listed ideas really help?
- Is there anything else i can do to keep my system cool?

Thanks in advance for your help.

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Hokusai's picture
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hmm

http://discussions.apple.com/thread.jspa?messageID=5028904

I don't own a MDD myself, but this post should help me thinks.

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Eudimorphodon's picture
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You're worried about 113?

I don't own a G4 desktop, but I'd guess that 113 degrees is *nothing*.

Freescale lists the PowerPC 7455 CPU as having a typical power dissipation rating (depending on speed) roughly between 11 and 19 watts. That much power is being dissipated by a chip of silicon metal about a centimeter square. Compare to, say, a 100 watt lightbulb, which is radiating about 6 times as much energy over a roughly spherical area of about... (back of envelope calculation...) 50-ish square centimeters. Even if we double the one square centimeter to two assuming that the silicon die radiates equally from both sides, the surface area-to-power-density ratio is... let's see... (50 /2) / 6 = 4-ish times more for the CPU chip then the light bulb.

I can say from experience that if you lay fingers on a 100 watt lightbulb that's been on for a while in a 65 degree F. room it usually manages to be a bit more finger-scorching then 113 degrees would be. Given the power density it's dealing with I'd venture the cooling system in your computer's doing a pretty decent job if it's keeping the CPU at 113.

Freescale lists the maximum "normal" junction temperature for the G4 as either 65C or 105C, depending on the model. 45C is a good chunk away from either of those. Also note that the onboard temperature sensor on those chips is notoriously unreliable. Unless your machine is constantly crashing and you've eliminated other more likely causes then heat I'd turn off the monitoring software and just live in ignorant bliss. But, of course, YMMV.

--Peace

TheUltimateMacUser's picture
Joined: Jan 28 2004
Posts: 615
thanks

Thanks for the replies guys... I'm currently in the process of reinstalling Leopard, to see if that solves my instability issues. For now i'll just keep an eye on the CPU temp from time to time, and we'll see how things go this spring & summer. Thanks again.

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Hawaii Cruiser's picture
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How to do you take its temp?

Umm, so what programs monitor CPU temperature? I helped my wife purchase a dual 1.25 MDD last month. It has made me realize that I'll not be getting one for myself because of the heat. I was surprised how much heat is being blown out of the back. It would turn the little room I do most of my computing in into a nice little sauna pretty quickly. It's still got that Radeon 9000 fanless card, and two 7200rpm drives stacked on top of one another on the ATA100 bus. I was thinking it would be good for her to have three hard drives in there: one for extra storage and one for backing up. I thought maybe a 5400rpm drive on the ATA66 bus for backup would be smarter heatwise, but maybe investing in firewire backup and storage is the only wise move. More expense, yippee! There's provision for four hard drives in the case, but how smart is it to have even more than one drive in there if you want the cpu to last a good long time?

How advantageous are those PCI slot fans? I remember reading a long time ago somewhere that the interior of the G4 towers is designed for optimal venting, and mods like PCI slot fans might disrupt the intended interior airflow. That sounded a bit bogus. You see these fan systems you can buy for Radeon cards that are actually the same thing as slot fans as they take up the whole next slot space with an on-card duct and blow heat off the GPU straight through that duct and out a vent in that next PCI opening. Since that system is all enclosed it wouldn't be disrupting any other airflows. Isolating each major heat generating component that way instead of relying on the big case fan seems like a strategy that would work wonders. Is the G5 case more like that? I've never opened one up.

TheUltimateMacUser's picture
Joined: Jan 28 2004
Posts: 615
Temp Monitor

Temp Monitor... google it... it works. It's basically a free version of Hardware Monitor, but it only does CPU temp reporting. It also comes with a CLI accessible version of it, which is what i use.

I think i may order one of those PCI slot fans (they are cheap enough anyway), and see if i can get my temp down a bit, as it should be a little cooler with my main case fan running full tilt. I also have an aftermarket fan there, as the OEM one was too frigging loud (although this one should be moving almost the same amount of air).

Anywhoo, to answer your other question, yes, the G5 separates out the major components into their own sub-enclosures for far better heat management.

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TheUltimateMacUser's picture
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Success!

My idle temp went from 41C down to 30.6C, just by enabling nap mode!

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eeun's picture
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How are your PSU fans for noi

How are your PSU fans for noise and flow?
I've seen a couple pages recommending replacing the built-ins with aftermarket fans that are both quieter and push more air.

The PCI slot fan should help, but I don't think you need to worry.

A lot of the air entering the MDD comes from a large opening at the bottom front of the case. Make sure there are no cables or dust bunnies obstructing flow.

...or you could always do an ATX upgrade Wink

FWIW, my temps are still hovering around 96F with ambient around 67F, so bump up the ambient and my G4 temps probably won't be much different from yours.

Quote:

My idle temp went from 41C down to 30.6C, just by enabling nap mode!

Oh, sure...switch to Celsius after I went through the trouble of converting my temps to foreign-heat. ;D

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OT: Celcius vs. F.

I remember the US was supposed to switch over to Metrics in 1980 and as I recall (I may not be correct, it was a long time ago) Regan squashed it with the statement 'It would be too difficult for older Americans'. I remember road signs with both kilometers and miles and people getting all confused and outraged over it.

I don't mind metrics. I don't mind the 'English system' (though the UK has gone metric too) but I HATE the mixture of both we have today. You know how long it took for me to find a tape measure that reads both English and metric? Finally found it at Home Depot for 50 cents!

It's like they keep saying the MacBook is 'less than one inch thin' Darn it, it is 25mm! Just about exactly 25mm! Just say it!!!

Floppy disks were NEVER 3 1/2" they were 90mm! (not sure about 5 1/4" disks), CDs, DVDs, BluRay are 120mm. I personally think 90mm is a better size but opinions are like...

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TheUltimateMacUser's picture
Joined: Jan 28 2004
Posts: 615
Re: How are your PSU fans for noi

eeun wrote:

How are your PSU fans for noise and flow?
I've seen a couple pages recommending replacing the built-ins with aftermarket fans that are both quieter and push more air.

The PCI slot fan should help, but I don't think you need to worry.

A lot of the air entering the MDD comes from a large opening at the bottom front of the case. Make sure there are no cables or dust bunnies obstructing flow.

...or you could always do an ATX upgrade Wink

FWIW, my temps are still hovering around 96F with ambient around 67F, so bump up the ambient and my G4 temps probably won't be much different from yours.

Quote:

My idle temp went from 41C down to 30.6C, just by enabling nap mode!

Oh, sure...switch to Celsius after I went through the trouble of converting my temps to foreign-heat. ;D

With the main case fan turned down a bit (im running aftermarket fans, and the main case fan speed is controlled via a knob), the noise is fairly acceptable, and with Nap Mode now enabled, the CPU temp is a bit cooler, so, i'll probably hold off on the PCI slot fan for now. We'll see what happens this spring / summer. I am aware the MDD is a bottom breather, and although it is on carpet, the bottom vent is unobstructed both inside & out, and the inside of the case is kept dust free as part of my regular maintenance.

Oh, and i switched to Deg Cel because that seems to be the preferred scale when dealing w/ CPU temps, for some reason.

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Hawaii Cruiser's picture
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52.6C

I finally got around to trying the Temperature Monitor application. I fixed a Zalman Silent Heatsink (no fan) on a Radeon 9800 Pro that I flashed to Mac, and then installed the card in one of my Quicksilvers (I can just barely shut the case closed with it in there--I have to reach in and nudge the 9800 as I close the case door so that the top fasteners on the heatsink can get past the bottom of the PSU), and I thought I should monitor the heat in there so I downloaded Temperature Monitor. Unfortunately, the only sensor in the Quicksilver is the hard drive SMART sensor. Sad Machines made before 2002 don't have sensors. Shucks. But I then went and downloaded the application to the MDD while my wife was away from it taking a shower, and it shows a CPU idle at 52.6C. The weather is actually pretty cool here this evening (lower 70's F, 20's C)--rain and wind. My mercury ambient temp monitor is in strong conflict with my personal lack-of-surfing-weather monitor. Undecided

I've still got the 9800 in this QS. Hopefully it's not melting while I'm typing this. No way to monitor it's heat except to shut down the QS, open it up, touch the heatsink, and hope I don't blister to the touch.

unknown1's picture
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I think you can buy temperature sensors...

But I think the display fits in a 3 1/2" external drive bay and if they have any software that monitors them I am sure it is PC only...

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Hawaii Cruiser's picture
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WOW! What a surprise! I shut

WOW! What a surprise! I shut down my QS, opened it immediately and felt over the Zalman heatsink. It was not only NOT superhot, it wasn't hot at all! I had to touch way down by the GPU area to feel any warmth, and it wasn't significant. Well, I guess it makes sense because when you fold up the case door the 9800 with this big heat sink is sitting right in front of the big case fan. Here's the heat sink:

http://www.zalman.co.kr/ENG/product/Product_Read.asp?idx=135

I had been thinking all along that I might put the card with the heatsink in the MDD so I went to check the spacing in the MDD. No way, there's no way you could put that heatsink in the MDD unless you were to remove the upper optical drive cage. I hadn't given the MDD that much of a close inspection before about how it all fits together. Even if you did remove the drive cage, the case fan is below the expansion cards. It doesn't look like its even blowing on them in any direct way. The only way you could get a fan blowing down on the heat sink--if you did remove the drive cage--would be to do Eeun's ATX PSU conversion:

http://www.applefritter.com/node/23451
http://www.applefritter.com/node/23857

With the OEM PSU out of the way, you could mount a fan there in its place to blow on the cards. Then you could get one of the quiet PSU's on the market too to also reduce noise, and find quieter models of fans to add--replacing the stock large case fan with a stronger quieter version. The large case fan's function is primarily for blowing across the huge CPU heatsink it seems, and somewhat for the faster hard drives.

I was thinking it was the PSU that was making most of the noise from the MDD, but looking more closely, I'm wondering where all the noise really does come from. There's the case fan, the PSU, and there's a smaller fan mounted on the door for the optical drives. The DVD drive itself has a small fan. Are there other fans? The MDD's inside design is quite different from any of its other graphite predecessors. It looks like the design department really worked overtime in order to not have to abandon the outer trademark G4 graphite case. It's really quite a contraption of ways to get the heat out of a tightly packed situation.