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Which temps should I trust?

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Old 06-03-04, 07:37 PM Thread Starter   #1
ap673
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Which temps should I trust?


Hello all, I was just wondering what temperature monitor should I trust. My motherboard gives me 44-47c, MBM5 gives me 36-38c, and Asus probe gives me 30c. What the hell? Theyre each a lot different, oya I have a A7N8X v1.06, xp2500, and SK-7. THanks!
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Old 06-03-04, 07:45 PM   #2
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Interesting...
I have a7n8x and probe and MB come up with same...
I dont have any solutions though..Im a nooob at this crap
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Old 06-03-04, 08:02 PM Thread Starter   #3
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hahaha, thanks anyway
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Old 06-03-04, 08:03 PM Thread Starter   #4
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Hey do u have a A7N8X non-deluxe v1.06?
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Old 06-03-04, 08:05 PM   #5
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nope.. delux..ver 2...sorry
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Old 06-03-04, 11:27 PM   #6
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I set shut down in bios for 75C and don't pay attention. You should'nt either.
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Old 06-04-04, 05:24 PM Thread Starter   #7
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Haha so u dont care about the temps?
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Old 06-04-04, 06:08 PM   #8
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No, what for? I mean I look at them to be sure I did'nt install HS or waterblock on upside down or backwards but beyond that I just go with whats recommended at the main site who uses accurate temerature diodes and stuff to meansure the best HSF. Boards themselves are notorious liars so I don't care what they say for the most part.
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Old 06-04-04, 06:14 PM   #9
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I have the -e Deluxe version of your motherboard, and I have no such problem. mbm and asus probe give me the same temps, and my enermax controller is about 2C under that. as long as the temps being reported arent all in the 60s, you should be fine.
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Old 06-04-04, 06:51 PM   #10
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I have the Asus A7N8X Deluxe v. 1.06. The temperature monitoring came in handy when my BIOS CPU temperature climbed to 78C one time.

Are you monitoring all the temps? I have these temperature settings:

Case: Asus 1
CPU Diode: W83L785TS-S Diode
CPU Socket: Asus 2

The BIOS CPU temperature seems to be closer to the "CPU Diode: W83L785TS-S Diode" one
The Asus Probe CPU temperature seems to be closer to the "CPU Socket: Asus 2" one

BTW, for voltages I found the "ABS100 Standard 2" to give reading more consistent with the voltages displayed in the BIOS.

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Old 06-05-04, 08:23 AM   #11
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Trust none of them The only use for temperature is seeing what happens as you change stuff. For example, if moving a fan results in a lower "CPU" temperature, then the CPU's probably running cooler. They're not much use for decidng whether your CPU is too hot or not, as there can be up to 20 deg C variation between boards. In general, if it's stable then it's not too hot (though if a temperature is reported as over 70 or so it probably merits a look to make sure everything is actually OK).
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Old 06-05-04, 08:33 AM   #12
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The colder the better, just use the best cooling you got and trust to luck =P
Most bioses have an alarm anyway, if it senses the temp going up it warns you, and yeah it sometimes shuts down. Rarely if ever does it cause damage. I dont think its a big thing to worry about =P
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Old 06-05-04, 09:03 AM   #13
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Quote:
Originally posted by hitechjb1
How to read CPU temperature

Temperature reading from temperature sensors, bios/software reading are error prone, i.e. absolute reading can be off significantly, by as much as few degree C. Then the question is how to comapre CPU temperature between different systems, different case cooling, different seasonal effects, between idle and load conditions, ....

The internal CPU die temperature monitoring device (aka diode) monitors die temperature. There is usually another temperature measureing device at the CPU socket, external and touching the CPU to monitor the CPU temperature. These two numbers would not be the same in general, the external one usually being lower under full load. Some motherboard bios and monitoring software can report both of these temperature for comparison, so these numbers can be tracked by using their difference. E.g. ABIT NF7-S reports only the external one, regardless of what software monitoring programs used (such as MBM5, hardware doctor), but the BIOS temperature cut-off protection indeed uses the internal die temperature for protection. The ASUS A7N8X can report both temperature numbers.

Four different temperature measurements can be measured for air cooling, and can also be extended to water cooling. It would be less error-prone and less dependent on the absolute accuracy of the on-board temperature sensors and software/BIOS probe.

CPU_fullload - CPU full load temperature
CPU_idle - CPU idle temperature (loosely defined, e.g. just boot up OS/BIOS, with minimal stuffs running)
SYS_fullload - system ambient temperature when CPU at full load
SYS_idle - system ambient temperature when CPU idle

actual_CPU_temperature_increase = (CPU_fullload - CPU_idle) - (SYS_fullload - SYS_idle)

So the absolute temperature of CPU is not read, but rather
- the difference between full load and idle, and
- the difference between CPU and system.
Hence eliminating (relatively) the absolute measurement errors, and ambient temperature effect.

E.g. CPU under simliar load in summer and winter, or under different ambient room temperature conditions.
Summer:
CPU_fullload = 53 C
CPU_idle = 42 C
SYS_fullload = 31 C
SYS_idle = 28 C
actual_temperature_increase = (53 - 42) - (31 - 28) = 8 C

Winter:
CPU_fullload = 40 C
CPU_idle = 29 C
SYS_fullload = 18
SYS_idle = 15 C
actual_temperature_increase = (40 - 29) - (18 - 15) = 8 C

This can apply to water cooling. Replace SYS_fullload with WATER_INTAKE_fullload_temperature, and replace SYS_idle with WATER_INTAKE_idle_temperature.


Advantage of using these four temperature numbers:

- It relatively eliminates the effect of absolute errors from the temperature sensors and software/BIOS reading.

- As the system temperatures are measured, it relatively eliminates the effect of case cooling on the CPU temperature measurement.

With this, one can compare the temperature change of two CPU's between idle and full load, even when the two CPU's are in two systems with different case cooling.

E.g. the CPU in a case with worse case cooling would tend to read a higher temperature, but the change in temperature should be similar to the one in a case with better case cooling (assuming the worse CPU did not crash first due to higher temperature).

- It also eliminates the effect of seasonal ambient room temperature on CPU temperature reading.


Power dissipation

power_dissipation = (CPU_temperature - system_ambient_temperature) / cooling_coefficient

For good case cooling, SYC_full_load - SYS_idle should be at most 2 - 3 C when CPU is under full load at 2.4 - 2.6 GHz on air.

For CPU under full load, using my CPU as an example,

Tbred B 1700+ DLT3C at 2.54 GHz 1.92 V,
CPU_full_load - CPU_idle ~ 8 C
CPU_full_load - SYS_full_load ~ 20 C
full load power ~ 20 / .22 = 91 W

For a mobile Barton at 2.65 GHz 2.15 V,
CPU_full_load - CPU_idle ~ 12 C
CPU_full_load - SYC_full_load ~ 27 C
full load power ~ 27 / .22 = 123 W
Quote:
Originally posted by hitechjb1
...
The higher the voltage and frequency, the higher the power and the higher the temperature. Such active power will increase the CPU to certain temperature under certain load for a given cooling.

Since carrier mobility decreases as temperature increase beyond certain temperature due to lattice scattering, transistor switching slow down as temperature increases. So the frequency f of a CPU varies inversely with the temperature, or df / f = - k dt, mathematically, where f is frequency, t is temperature, and k is a constant.

The balancing of these two opposing actions, or the intersection of the voltage-frequency curve and the temperature-frequency curve of a CPU characteristic naturally determines the final stable voltage/frequency/temperature operating point. If overclocking is done properly, the maximal overclocking should settle naturally at certain frequency, voltage and temperature, as desribed above, below the maximum absolute rating of voltage and temperature (as seen from Tbred/Barton, ...). A perceived stable voltage and temperature setting may not be necessary after all, if the voltage, temperature, frequency variations are monitored properly and adjusted incrementally.

CPU voltage: from stock to max absolute, from efficient overclocking to diminishing return (page 19)
What is an ideal and safe temperature for overclocking (page 19)

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Last edited by hitechjb1; 06-05-04 at 10:30 AM.
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