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Since87 · 05-13-2003, 11:24 PM

The only way I can think of to measure the current, and not totally compromise the CPU's ability to run at high speed, is as follows:

Take a sheet of copper that is thin enough that it can fit between the CPU and socket without interfering with the socket connections, yet thick enough it can be drilled without folding up completely. (Maybe 0.030")

For each Vcc pin location, drill a hole with an ID just slightly larger than the CPU pin.

For all other pin locations drill a larger hole so that there is no risk of shorting the pin to the foil, but there is still a substantial mesh of copper.

Place the drilled sheet of copper over the CPU pins.

Solder all of the Vcc pins to the copper sheet, and cut them off flush with the sheet.

Remove the electrolytic capacitors on the motherboard which are connected to the Vcc regulators. Reinstall them on the backside of the board.

Install the cpu with attached copper sheet into the socket.

At this point you need to prepare a very short heavy wire to connect between the Vcc pin of the electrolytic capacitor, and the copper sheet. This heavy wire has to have two smaller wires attached to it near either end. This gives you a 4-wire (Kelvin) connection to a length of wire having some resistance. (1 inch of 10 gauge wire would give you 83 uOhms, so with 50 Amps going through it you would measure about 4 mV.)

Before soldering the heavy wire into place. Measure the voltage drop between the two smaller wires with 10 Amps flowing through the heavy wire. This allows you to calculate the resistance of the heavy wire between the two smaller wires.

Now solder the heavy wire into place. (Don't allow the connections of the smaller wires to change while you do this.)

Connect additional 10 gauge wires between the Vcc pins of the other electrolytic capacitors, and the one to which your 'resistor' is connected. (These additional wires are to keep the full current of the CPU from being pulled from the pin of one electrolytic capacitor.)

Do this, and there's some chance the setup will actually run and allow you to measure the current. I think there is likely to be a problem of inadequate decoupling capacitance between Vcc and ground that prevents stable operation. Space constraints make it hard to do much about this though.

So THG claims to have measured the current draw of an operating CPU? Unless AMD provided them with the test setup, I don't believe it.

05-13-2003, 11:24 PM	#49
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	The only way I can think of to measure the current, and not totally compromise the CPU's ability to run at high speed, is as follows: Take a sheet of copper that is thin enough that it can fit between the CPU and socket without interfering with the socket connections, yet thick enough it can be drilled without folding up completely. (Maybe 0.030") For each Vcc pin location, drill a hole with an ID just slightly larger than the CPU pin. For all other pin locations drill a larger hole so that there is no risk of shorting the pin to the foil, but there is still a substantial mesh of copper. Place the drilled sheet of copper over the CPU pins. Solder all of the Vcc pins to the copper sheet, and cut them off flush with the sheet. Remove the electrolytic capacitors on the motherboard which are connected to the Vcc regulators. Reinstall them on the backside of the board. Install the cpu with attached copper sheet into the socket. At this point you need to prepare a very short heavy wire to connect between the Vcc pin of the electrolytic capacitor, and the copper sheet. This heavy wire has to have two smaller wires attached to it near either end. This gives you a 4-wire (Kelvin) connection to a length of wire having some resistance. (1 inch of 10 gauge wire would give you 83 uOhms, so with 50 Amps going through it you would measure about 4 mV.) Before soldering the heavy wire into place. Measure the voltage drop between the two smaller wires with 10 Amps flowing through the heavy wire. This allows you to calculate the resistance of the heavy wire between the two smaller wires. Now solder the heavy wire into place. (Don't allow the connections of the smaller wires to change while you do this.) Connect additional 10 gauge wires between the Vcc pins of the other electrolytic capacitors, and the one to which your 'resistor' is connected. (These additional wires are to keep the full current of the CPU from being pulled from the pin of one electrolytic capacitor.) Do this, and there's some chance the setup will actually run and allow you to measure the current. I think there is likely to be a problem of inadequate decoupling capacitance between Vcc and ground that prevents stable operation. Space constraints make it hard to do much about this though. So THG claims to have measured the current draw of an operating CPU? Unless AMD provided them with the test setup, I don't believe it.