Locating VCC (vCORE) Read Point

[poldopunk]

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Image taken from The Tech Repository.

Spoiler! 

Hi everyone, this is an image created by Kris Boughton before he was picked up by Anandtech, its a good representation of the VRM (voltage regulator module) in the motherboard as such that it instead of using symbols, it uses actual representation of the components (PWM controller, MOSFET drivers, MOSFETS, inductors (chokes) and capacitors). I created a thread here to ask electronic experts a question.

This is regarding taking voltage readings of the power supplied to the processor. Now, most people would quickly say, probe one of the feet of the MOSFETS to get a reading but I don't think its a good idea because the MOSFETS switches on and off through the PWM a hundred if not a thousand times per second to lower down the voltage from 12-volts to the VID required by the processor. So one needs to have a very good digital multimeter to get an average of the entire sequence. My questions are the following:

• Can I take the reading from the inductors (chokes) or the capacitors?
• If so, do these components have charges (positive/negative) that might damage the unit if I probe into the wrong charge?
• Where would you suggest other reading points if these two are not an option?

I know where the readouts for my board (EP45-UD3R), courtesy of Clunk.org forums but I'd like to apply this little theory to generic or other motherboards as well.

EDIT: I forgot to add the fact that motherboards with ferrite chokes don't have their feet on the front but through the back so medyo lisod mag take ug reading sa inductors but its doable.

[limes]

@poldopunk murag risky man kaau ni, ok ra especially if you really know what you are doing. considering na very sensitive ni na mga devices kay microprocessors naman ni sila dako kaau nig effect if ma timingan og ka sayup. it could provide tension sa specific part that could cause it to malfunction and worse work abnormally. reading voltages also causes slight voltage drops katong mga ECE ug mga EE dira post na mo ug ma recommend ninyo na sure jud kay na paksit jud ni basta ma sayup.

[poldopunk]

risky if you have shaky hands and don't know how to use multimeters. i've already tried several times taking readings from the mosfets for the NB voltage, i just want to make sure kung ok ra ba sa parts nga akong gimention for the processor.

no guts, no glory bai.

calling master simoko!

[poldopunk]

yohoo! sir yoyong, mata pa ka?

[MogLetz]

kuyawa mga trip oi

[ethzneuron]

i'll try to answer pero i'm not into OC ha.. hehehe, so pwedi ra pod i-skip ni ninyo nga post.

Q1:: Can I take the reading from the inductors (chokes) or the capacitors?
depende sa location, preferred ang accessible. sure gyud ning solid cap nga naa sa luyo, pero dali ni siya i-probe kay dako. ang pagtultol nalang asa sa luyo..

Q2:: If so, do these components have charges (positive/negative) that might damage the unit if I probe into the wrong charge?
inductors kay walay polarity, no harm done..
electrolytic caps kay naa, no damaged done kung mag-probe ka sa opposite lead niya..
(basta lang ang other pin/ negative probe sa multimeter kay naa sa ground!)

Q3:: Where would you suggest other reading points if these two are not an option?
is vcc and vcore the same? if so, pwedi seguro ko sa vcore mod/sense feedback.. ang problema lang ani kay kung ma-short pag probe maguba nya ang pwm controller. you can use the leg of the pwm controller to test if walay lain location.

lain location kay sa tiil sa mosfet.. if ang prob kay switching a gazillion times. your dmm will just read it as 3.3V or 5V.. tungod sa kapaspas, ig read niya mura nalang ni og straight-line dc, not the pulsating one.

[poldopunk]

thank you for your answer. i guess i needed an affirmation if it would kill the motherboard if i stuck in the test leads at the wrong polarity.

i'm using three ground points; ground sa fan header, ground from the power supply (black wires) or ang chassis itself so far, wala man difference pero the fan header gives the best and closest reading of them all. VCC is the proper term for the voltage supplied to the processor or a specific component in this case, isolated raman sa VRM for the processor so pwede ra bali-balihon. once again, thank you for answering the question.

**EDIT**

I was surfing around and found an article sa XS. sakto jud diay akong theory nga dili advisable mag read from the FETs tungod sa switching, this is their recommendation (blue):

Spoiler! 

a classical example!

Spoiler! 

Some Important information on measuring your cpus voltage. - XtremeSystems Forums

[simoko]

@ poldo: ka atots gyud nimo oi...bisan unsa man lang imong ukai-ukayon diha...to make a very long explanation short:

- Can I take the reading from the inductors (chokes) or the capacitors? NO
- If so, do these components have charges (positive/negative) that might damage the unit if I probe into
the wrong charge? qualified YES
- Where would you suggest other reading points if these two are not an option? NONE

today's VRM/VRD10.x guidelines employs a 6-bit "voltage identity" or VID code that controls its output voltage from 0.8375 to 1.6 V dc. Regardless of the approach, the six VID code pins on the VRM/VRD connect to the corresponding pins on the microprocessorVID pins. Internal coding within the microprocessor then controls its applied voltage. VRM/VRD guidelines set the voltage tolerances of the initial dc output voltage set-point error, output ripple and noise, no-load offset centering error, current-sensing, droop errors, and dynamic load limits.

it works like this:the voltage regulator module (VRM) receives a voltage identification (VID) signal from a CPU to supply the CPU with a core voltage corresponding to the VID signal, the VRM comprising: a core voltage generator which generates the core voltage; and a voltage regulation control unit which determines a percent voltage regulation of the core voltage based on a spec signal from the CPU to control the core voltage generator to generate the core voltage having the percent voltage regulation corresponding to the spec signal. the voltage regulation control unit comprises: a programmable register which outputs a percent voltage regulation compensation signal to compensate the core voltage, based on the spec signal; and a PWM signal generator which outputs a PWM signal to control the core voltage generator to generate the core voltage having the percent voltage regulation corresponding to the spec signal, based on the percent voltage regulation compensation signal from the programmable register.

in short...wala kai accurate voltages ma measure dha kai switching na sya...its also the reason why controlling vdroop is not good & will result into higher power consumption...hahahaha...na-intriga ka?

by the way...dili lagi ko master...MO slave ra...

[poldopunk]

grabeh ang explanation, i had to read it several times para ma absorb.

i'm not looking for VID, ang current VCORE lang nga gi supply sa board. i'm basically trying to match if the set voltage in BIOS is equivalent to the supplied voltage by the VRM.

[simoko]

if you can locate the VSS_SENSE & VCC_SENSE pins of your particular processor then that is the best point to measure the voltage received by the processor core...but you have to get your processor's specific datasheet for the correct info...

pwede pud through the Super I/O chip nga gamit sa imong mobo...one of the eight voltage channel pins diha has a trace line connected to the vcore thingy...refer to the datasheet of your particular SUPER I/O chip...(this is where Everest/Superfan etc. utils get their readings)

BE EXTRA CAREFUL.....as measuring these things require that the system is ALIVE & you get the measurements at the pinouts at the back of the mobo...