Ambient temp sensor on 09 Mac Pro

[rexie]

Hi All,
My Mac Pro 1,1 was stolen and was replaced with a 2.66 Oct '09 Mac Pro. Have noticed that the temp sensor is way off, up to 8 deg C! My old Mac was accurate for ambient temp no matter what the load was on the computer. On the new Mac on startup it's 2 to 3 degrees too hot then increases. Anyone know where the sensor is?

[inigel]

Not to pick or anything, but how did you determine it was inaccurate?

[seadragon]

Mine is also quite inaccurate. Room temp is 22C and ambient reads 31C.

[UltraNEO*]

Hi All,
My Mac Pro 1,1 was stolen and was replaced with a 2.66 Oct '09 Mac Pro. Have noticed that the temp sensor is way off, up to 8 deg C! My old Mac was accurate for ambient temp no matter what the load was on the computer. On the new Mac on startup it's 2 to 3 degrees too hot then increases. Anyone know where the sensor is?


Unless Apple changed it, the ambient temp sensor should be in the top section, above the optical drive (at least that's where it is on the 08 MP).

This area should be the coolest part of the MP. Take out the optical caddy and look, it's black and glued to the case!

[Eithanius]

@inigel

Because we have 2 Mac Pros with the right software to compare.

TS,

I noticed the same problem here. I had a MacPro2,1 before it got replaced with a MacPro4,1. Basically the ambient temperature on the new Mac Pro registers a higher ambient temp compared to the older model. 27 degrees C on the old MP against 35 on the new...

[UltraNEO*]

I noticed the same problem here. I had a MacPro2,1 before it got replaced with a MacPro4,1. Basically the ambient temperature on the new Mac Pro registers a higher ambient temp compared to the older model. 27 degrees C on the old MP against 35 on the new...

Out of curiosity, why is it important?

[Eithanius]

Out of curiosity, why is it important?

Out of curiosity of course...

[justflie]

I would assume that the case fans' rpms are tied to ambient temp in the case. If it's significantly higher, the fans would probably speed up unnecessarily.

[ManiG]

Same "issue" here, 2009 MP. The ambient consistently shows 6-7 degrees Celsius above the "actual" ambient temperature in my office.

Not important though, as mentioned just a curiosity. :)

[UltraNEO*]

Out of curiosity of course...

Since it's attached to the inside of the case, how about attaching a thermo sensor to the exterior of the case? Say under the handle above the optical drive, that should be the direct opposite side, no?

Actually, I wouldn't be surprised the ambient temps to be higher than room temps, this is because it's the highest part of the enclosure; physics tells us heat rises.

[nanofrog]

Actually, I wouldn't be surprised the ambient temps to be higher than room temps, this is because it's the highest part of the enclosure; physics tells us heat rises.
Ambient may be the internal air temp of the MP, not the room, depending on specific location. At the top of the case makes the least sense IMO, as that's not what being drawn across the cooler/s.

Ideally, I'd think they'd have placed the sensor in the intake section (just after front fan/s) for the CPU/s to get the most accurate reading, and applicable to the air entering the CPU coolers.

Fans should be tied to the core temps, not ambient btw. ;) The reason is simple. Cold ambient, say during winter, yet the cores are roasting (really hot under full load). If the fans are tied to the cold air, they won't ramp up, starving the coolers for the cold air needed during the high load period. :)

[Tesselator]

I think they got it right and the Ambient sensor should be right where it is. The ambient sensor tells the system that the exhaust fans are ejecting enough heat or not. If they aren't the heat at the top will increase to considerably above room temp. If they are then Ambient will be within a degree or two of the room temp.

The CPU (or RAM, HDD, et.) fans are in charge of cooling that part. If that used (heated) air isn't being ejected fast enough then the above sentence kicks in.

[nanofrog]

I think they got it right and the Ambient sensor should be right where it is. The ambient sensor tells the system that the exhaust fans are ejecting enough heat or not. If they aren't the heat at the top will increase to considerably above room temp. If they are then Ambient will be within a degree or two of the room temp.

The CPU (or RAM, HDD, et.) fans are in charge of cooling that part. If that used (heated) air isn't being ejected fast enough then the above sentence kicks in.
I was thinking in terms of the CPU/mem chamber. Ambient in the intake fan region, and of course the CPU core diode as well. If exhaust heat cycles around internally, the core sensor will pick it up (gets sucked back in the cooler/s), and kick in the exhaust setting, even if ambient hasn't shifted at all. It's not that complicated actually.

A simpler design is to monitor the overall case temp, which is likely what they're doing (also cheaper). But given the different chambers, you'd really need one per to get accurate data for each, and controll any intake and exhaust fans for each as well.

[rexie]

Thanks for the replies.
To be honest, the reason I asked is I like seeing the room temp in the menu bar! I could buy a cheap temp sensor and sit on my desk but I didn't need to with my old Mac pro. Don't like this hyper-threading either with current programs, but that's another story!
Cheers.

[nanofrog]

I could buy a cheap temp sensor and sit on my desk...
That's what I do anyway. :)

[slicecom]

Same issue here. My MacPro 1,1 is accurate and my bosses MacPro 4,1 in the same room reports the ambient temperature consistently up to 7C higher than reality (and the accurate temperature on my 1,1).