Intel has a
weblink meant for resellers (i.e. OEMs) that indicate what TDP rating needs what type of PSU rating, towards the middle is the following:
04A(84W),04B(116W) -- 12V2: 13A continuous
05A(95W) -- 12V2: 13A continuous and 16.5A peak for at least 10ms.
05B(130W) -- 12V2: 16A continuous and 19A peak for at least 10ms.
06(65W) -- 12V2: 8A continuous and 13A peak for at least 10ms.
Looking at the last line, it says a 65W TDP rating requires 8A from 12v continuously and up to a 13A requirement at peak. Why 12v? Because that is what the CPU cores and cache uses on a separate CPU power cable from your PSU, that is what changes the most when you overclock; the other controllers and circuity may use 5v and 3.3v, but not as much as you think. Since your CPu and GPU uses the most power in your system, and from 12v, that is why you focus on 12v requirements only when looking for a new PSU. The only way the other voltages matter is if you are putting a low-power rig together, then the CPU+GPU isn't the majority anymore.
Either way, Intel already figure out what you need to look out for in the above ratings. Granted, not every TDP rating is included in that short list, so you'll have to extrapolate for the TDP rating you want to look up. I've done the math for you but it is simple algebra, usign the above numbers to scale, here is a formula for both continuous and peak:
- Continuous 12v Amperage = 0.123 x TDP
- Peak 12v Amperage = 0.0923 x TDP + 7
Using these formulas, the 140W TDP rating of Haswell-E a minimum of 17A continuous with 20A peak for any processor with the same TDP rating.
Caveats:
- Because overclocking would affect wattage exponentially with frequency and voltage, and because no two processors have identical quality, you can't use Intel's numbers for overclocking power requirements. It is stock only. Is there an overclocking power formula? Yes, but it requires the stock value to scale everything by, and Intel never publishes those numbers. You would need a potentiometer to measure voltage and ammeter to measure amperage, then multiply the numbers to get the power draw. Software isn't accurate, you need to go out and measure it (or find a review where someone else already did that with Haswell-E).
- TDP (Thermal Design Power) is not actual per each processor since that would depend on number of cores, cache, and frequency. It is also not a consumption rating since the 16A minimum of 130W TDP turns out to be 192W of power (16 x 12 = 192, not 130). Since 192 is greater than 130, TDP isn't how much energy the processor uses, it is the maximum of how much energy it dissipates as heat. Likewise, the 140W TDP rating of Hawell-E is just that, a rating, it has nothing to do with how much power the processor needs or how much heat it actually gives off. Otherwise we could assume 140W ÷ 12v = 11.7Amps for the processor, which is BS. The only way to determine the heat dissipated off the processor is to measure it with a calorimeter (which is either a calibrated heatsink or a liquid cooling loop without the radiator so you can measure temperature increase of fluid over time, and then just use the heat equation).
post edited by lehpron - 2014/09/16 17:04:12