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AMD Motherboards & CPUs Questions or comments on AMD products?


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  #1 (permalink)  
Old 18th June, 2003, 02:50 PM
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Post Measuring power taken by an AMD processor

I am embarking on a project to measure exactly how much power AMD processors draw to aid me in writing up my heat dissipation article. I wasnt pelased with the new one so its been re-written but id prefer to colelct primary data for myself instead of relying on secondary data (other peoples data) as i am now as this would make the article much better.

Basically, I need help in working out how to do it. Basically, my idea is to have a motherboard. Secondly have a sepoarate Zif socket where the processor being measured will be in. This zif socket will conenct to he one on the motherboard and a True RMS meter conencted to the relevant pins I need to, to measure the power.

What do you guys think?

Thanks,
Craig
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Old 18th June, 2003, 05:06 PM
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Just a suggestion. It would be much easier to get these figures from AMD. Of course, they probably don't publish these figures for overclocked processors!
A consideration is that solder traces that go from the ZIF socket to the components on the mainboard are "tuned." Their length is calibrated.

Dang, there must be a way to do what you want mathematically!
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Old 18th June, 2003, 05:08 PM
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There is mathematically however its hard to find a formula that include both worst cases and non-load thus i want to get the fugures myself. Also, i need to get some overclocked figures which AMD couldnt and wouldnt supply.

Thanks for your reply, your the only one so far who has on any forum come up with a good reply, thanks!

Craig
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Old 18th June, 2003, 09:33 PM
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Another consideration is that CPU's suck an amazing amount of Amperage from the power supply. Enough to kill you many times over, personally I'd be loathe to get busy with Multimeter probes in that forest of pins. I think there's enough Amperage to make a direct measurement out of the question. Ammeters enclose the insulated wire to get their measurement. "Touchy-feely" is simply unsafe, IMHO.

Then again, I don't know how CPU's distribute their thirst for deadly Amperage among their pins.
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Old 18th June, 2003, 09:34 PM
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So it actually isnt safe to do this?

Craig
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Old 18th June, 2003, 09:57 PM
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If the 30+ Amps were in only two or three wires, direct contact would be avoided in all cases. There is a magnetic loop or similar in the two insulated "pincers" that enclose an insulated wire when using an Ammeter. The strength of the magnetic field around the wire/s is strong enough to gauge how many Amps are being drawn through it, boy howdy.

Supplied power is drawn through many of the pins of a CPU. There's no way that a single pin can withstand 30+ Amps. TBH, I don't know how you'd measure this! Perhaps the amount of current that a single pin draws can be used to extrapolate the entire amount?
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Old 18th June, 2003, 09:58 PM
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To be honest im not sure which is why ive posted, to try to gather as much info as possible along with trawling through every AMD white paper I can find and a lot fo reviews/articles on other sites.

Craig
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Old 18th June, 2003, 10:02 PM
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Glad to be of help! Unfortunately, my knowledge of the ways of our pal the electron is very incomplete.
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Old 18th June, 2003, 10:03 PM
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cloasters, thanks for the help its appreciated, who is this forums resident electronics expert please?

Craig
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Old 18th June, 2003, 10:10 PM
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We have very knowledgeable Members, thank goodness! At the drop of a hat, I'd say that surlyjoe and Aedan really know their stuff. These guys amaze me. We're lucky to have them!
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Old 18th June, 2003, 10:17 PM
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Thank you very much, I will drop them a PM.

Craig
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Old 19th June, 2003, 09:21 AM
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Your original idea won't work! As Cloasters correctly points out, you'll really screw the bus up by trying to wire in an additional socket! Those traces are designed with specific flight times and impedences in mind, and extending them could cause all sorts of horrible problems if it's not done right.

However, there may be a better point to look at: The CPU voltage regulator. It sits between the PSU and the CPU, and is of a simpler design, and less likely to object to being played with. The most difficult part is the fact that most CPU voltage regulators are more than one phase.

This means that you might have to do some serious soldering work in order to insert your measuring device between the PSU and the supply side MOSFETs.

Be aware that the waveform present on at the CPU regulator will be a complex waveform at high frequencies. However, on the PSU side, it should be much more DC than AC. Ensure that your meter can handle this situation, as the waveform is most definately not sinusoidal.

Áedán
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Old 19th June, 2003, 11:45 AM
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Thanks you very much. I was investigating last night whether or not I would be able to use the MOSFETs for this.

What would be the best type of meter to use please?

Craig
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Old 19th June, 2003, 12:23 PM
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Well, the meter you have might be able to do it! Check to see what it's limitations are!
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Old 19th June, 2003, 03:22 PM
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I dont have a meter, digital multimeter do? I was told a True RMS meter would be best.

Craig
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Old 19th June, 2003, 08:05 PM
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A true power meter would be good - I'm assuming that "True RMS" actually means true power. There's a certain level of confusion as to what exactly is meant by True RMS.
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Old 21st June, 2003, 05:54 PM
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The only way I can think of doing this is....

Take a board and mod it.
Unsolder one end of the output coils of the voltage regultion and add a loop of low guage fat wire between them.

Then use a clamp type ammeter to measure the current flowing.
My dad uses one of those meters of forklift trucks, that also pull high amps.

I did think about ading a shunt into the system and just measuring the voltage drop, however this is a bit impractical as the voltage is so low. You will only want a 0.1v drop (or less idealy) before the CPU max which means a very accurate voltmeter and a VERY low resistance shunt. Ive looked into it and its just not very practical.

Unfortunately those clamp ammeters are pretty expensive.
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Old 23rd June, 2003, 08:46 AM
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Quote:
Originally Posted by Holst
The only way I can think of doing this is....

Take a board and mod it.
Unsolder one end of the output coils of the voltage regultion and add a loop of low guage fat wire between them.

Then use a clamp type ammeter to measure the current flowing.
My dad uses one of those meters of forklift trucks, that also pull high amps.

I did think about ading a shunt into the system and just measuring the voltage drop, however this is a bit impractical as the voltage is so low. You will only want a 0.1v drop (or less idealy) before the CPU max which means a very accurate voltmeter and a VERY low resistance shunt. Ive looked into it and its just not very practical.

Unfortunately those clamp ammeters are pretty expensive.
Looks beyond my skill
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