Basics of Electricity, Circuits, Transistors, Processors, and CPU Temps

[(sin)morpheus]

That still doesn't explain things much, where does the 70A of current come from? I'm pretty sure the TDP is more than just power draw.

[undefeatedone]

70A comes from the 1.4V and the 0.02 Ohms of resistance the silicon, resistors, circuits, and transistors put up in the chip.

[(sin)morpheus]

I know how you got it. What I'm saying is where does that current come from, have you seen how much current the 12v line on a psu can put out?

[undefeatedone]

Good question. However, after thinking for a while, I think I have the answer. Amperes isn't a measure of power over time, which is what you are thinking of. Watts is. Lets say we have a 12V line and 34A. 12V * 34A = 408W. Now 1.4V times 70A is 98W. 98W is less than 408W. Confusing, but that is the only possible way it could work.

[(sin)morpheus]

Yeah, but it doesn't quite work still. Ohm's law states that voltage, power and amperage are all proportional to each other. Wattage isn't measured over time unless stated, otherwise ohm's law wouldn't work. For example, hydro bills. They charge you based on kW/h. 1kW/h is 1kW drawn for a period of 1 hour without stopping. See what I mean? 12V*34A=408W but your cpu doesn't use 12V, it's uses 1.4v which means it needs alot more amperes to get the desired amount of power from the 12V rail.

[undefeatedone]

Wattage is in fact measured over time. When it is assumed it isn't, its 1 second, because an ampere is an amount of current passing a point over 1 second, and A * V = W. However, a KW is a different unit of measure. It is 1000W. 1000W * 60 * 60 is 3,600,000W. So electric companies charge you based on every 3,600,000 watts. Its similar to how you get clockspeed. You dont multiply the Multiplier by the Hz, you multiply it by MHz.

[(sin)morpheus]

Whoops, my mistake on forgetting what a watt actually is, I must be rusty.
Though we still haven't solved the mystery of the missing amps, so to speak.

P.S. I know how to do math, I just forgot the meaning of a watt.
Actually on the note of math, you can multiply by the Hz rather than the MHz and it means exactly the same thing, the only difference is reduced numbers. 2.0GHz=2000MHz=2000000Hz. So it really doesn't matter whether I multiply by Hz or MHz (W or kW in this case), I end up with the same result. I could say that the power company bills me for every 3.6MW or 3600kW rather than 3600000W.

edit: The only solution I can think of is a step-down transformer, but it would take up a large amount of board real estate.

edit2: After flipping through some tech docs I have determined that a transformer is the only answer. The problem is I see no sign of a transformer on the motherboard I am examining. Any ideas on what else it could be?

[Sephious]

You silly people and your uppercase "K"s. Kilo is a lowercase "k" .

[(sin)morpheus]

Yeah, just usually do uppercase by force of habit. I fixed all mine so you can stop complaining about improper SI unit symbols!

[ether.real]

There is a transformer in your PSU. The line going into your PSU is AC, I believe it is stepped down to 3.3V, 5V and 12V with transformers, then it is converted to DC through diodes and band pass filters. However, this doesnt explain the amperage through the CPU because the Pin=Pout in a transformer. No power is gain or lost, except a small amount for heat and coil resistance. so if max Pout=400W, max current in on a 110V line = 400W/110V= 3.6A. Imagine how fast your breakers would trip if you were pushing 70A. Most breakers are 15A, 20 max. Think about how many computers you run on a breaker at a LAN party. 5 if you are lucky, and there is nothing else on the breaker. Where they get the TDP numbers is a mystery to me.

[onewecallgod]

Originally Posted by (sin)morpheus

After flipping through some tech docs I have determined that a transformer is the only answer. The problem is I see no sign of a transformer on the motherboard I am examining. Any ideas on what else it could be?

variable resistors are the "transformers" on the motherboard. the real transformer, as ether.real has stated is the PSU.

[ether.real]

Originally Posted by onewecallgod

variable resistors are the "transformers" on the motherboard. the real transformer, as ether.real has stated is the PSU.

variable resistors are transistors not transformers. Been reading up on this a little. Once the voltage has been stepped down in the PSU, it is rectified and filtered into a DC current flow. After this, it can be stepped down further using resistors and transistors.

If Pin=400W, then Pout=400W. If Vin=110V, and the whole transformer is dedicated to stepping down the voltage to 12V, then Iin=400/110=3.63A. Iout=400W/12V=33A. Not nearly enough to max out TDP.

Now lets assume that 110V is stepped down to the vCore of 1.35V. Iout=400/1.35V=296.3A. Now all this assumes that the CPU will draw the max Amperage that the PSU can deliver, which obviously, it wont. I beleive intel/AMD assumes an average resistance/current draw of their transistors, and I assume that the CPU probably uses multiple voltage lines, who knows what is vCore, 12V, 3.3V and 5V.

So in other words, I was wrong initially, 70A can easily be generated with a small enough secondary winding on the transformer

[onewecallgod]

Originally Posted by ether.real

variable resistors are transistors not transformers. Been reading up on this a little. Once the voltage has been stepped down in the PSU, it is rectified and filtered into a DC current flow. After this, it can be stepped down further using resistors and transistors.

thats why i put it in quotes. theyre not transformers, but they do "transform" the voltage down. what i to know is how efficient the stepdown vcore resistors are. they must be pretty **** efficient to keep our PSUs from being ******edly powerful

[ether.real]

kind of ambivalent wording if you ask me. You dont really transform DC, you transfrom AC. With a transformer. With DC you just let some of the voltage drop over a set resistor value. Lets try not to confuse n00bs too much :P

[mad_man]

basicaly, to get the same Wats on lover Volts u need more Amps
like
1.5V*80A=120W
12V*10A=120W

[undefeatedone]

Originally Posted by ether.real

variable resistors are transistors not transformers. Been reading up on this a little. Once the voltage has been stepped down in the PSU, it is rectified and filtered into a DC current flow. After this, it can be stepped down further using resistors and transistors.

If Pin=400W, then Pout=400W. If Vin=110V, and the whole transformer is dedicated to stepping down the voltage to 12V, then Iin=400/110=3.63A. Iout=400W/12V=33A. Not nearly enough to max out TDP.

Now lets assume that 110V is stepped down to the vCore of 1.35V. Iout=400/1.35V=296.3A. Now all this assumes that the CPU will draw the max Amperage that the PSU can deliver, which obviously, it wont. I beleive intel/AMD assumes an average resistance/current draw of their transistors, and I assume that the CPU probably uses multiple voltage lines, who knows what is vCore, 12V, 3.3V and 5V.

So in other words, I was wrong initially, 70A can easily be generated with a small enough secondary winding on the transformer

pretty much what I said, because V * A = W, so the only logical explanation for a cpu to use 100 some watts at a voltage of 1.4 is to use around 70A, and this is within the power that the psu can supply, it just needs to be regulated and changed.

[(sin)morpheus]

Yeah, but a resistor doesn't serve the same purpose as a transformer. A transformer has little loss in stepping down the voltage, a resistor has alot of loss from stepping down the voltage and the current will stay the same with them. So, the issue still is, where are they hiding the transformer?!

[ether.real]

The transformer is in the PSU as I previously stated.

[(sin)morpheus]

Thank you captain obvious.

We all know there is a transformer in the psu, but it only gets the voltages to 12V, 5V and 3.3V. We all know the cpu gets it's power from the 12V rail, but it has to step all the way down to 1.4V for a fx-57. The problem is the only device I know that can turn 12V 9.2A into 1.4V 70A is a transformer. There is no sign of a transformer on a motherboard.

[ether.real]

Refer to the Following picture:




I do beleive that the green loops with the copper coils to the left of the CPU may well be a transformer or two. Esp. considering that they sit directly between the 12V power plug and the CPU socket. Any thoughts? The only thing I dont understand is, i thought you could only transform AC. Everything is DC by the time it reaches the motherboard.