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Haswell Guide: Thermal Profile, Power Limit, "Safe Voltage" (vs. Ivy Bridge)

post #1 of 3
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Taken from Intel publicly available datasheets.

Source Material:

Haswell:
http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-desktop-vol-1-datasheet.pdf
http://hwbot.org/news/9347_intel_haswell_overclocking_fully_disclosed_theory_for_core_i7_4770k/

Ivy Bridge:
http://www.intel.com/content/dam/www/public/us/en/documents/design-guides/3rd-gen-core-lga1155-socket-guide.pdf
http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/3rd-gen-core-desktop-vol-1-datasheet.pdf

Thermal Profile:

What it is: Applying heaters (thermal test vehicles) to the die to simulate processor activity (cores, uncore, etc) and measuring with temperature probes the heat at different points in the chip. It's a lot more complex/precise test than this one line explanation implies, with the "instruction manual" spanning hundreds of slides for each product generation.

Ivy Bridge: T_case (deg. C) = .29 * power (W) + 45.1

Haswell: T_case (deg. C)= .33 * power (W) + 45.0


What this means: at the same wattage of power consumed by the chip, Haswell will be hotter than Ivy Bridge (.33 vs .29)

Power limit:

What is it: The power limit for the cihp based on Intel specs (for turbo boost). BIOSes are allowed to override this value. This is diffierent than the maximum operating temperature of the chip (thermal throttling). There is also a current limit specified, which seems to be more important than voltage limit.

Ivy Bridge (77W package):

(Core) Voltage Limit: 1.52V
Power Limit: Unspecified
Current Limit: 112A


Haswell (84W package):

(Core) Voltage Limit: 2V (IDF 2013)
Power Limit: 153W
Current Limit: 95A


Voltage Limit (calculate) = 153 / 95 = 1.61V


What this means: In theory, Haswell has a higher safe voltage than Ivy (1.61 vs. 1.52).
Edited by dr/owned - 6/4/13 at 12:06am
post #2 of 3
Nice find
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post #3 of 3
If that's the same data sheet that's been around for ages, that 1.52V is the highest VID the chip has a code for. It has no bearing on the "safe" voltage, which Intel has never specified.

And I don't think I'd put my faith in figuring the max voltage by calculating it from the max current and max wattage limits. I don't think Intel specifies them with that in mind. For example, do those limits include power draw from the iGPU?
Edited by Forceman - 6/18/13 at 1:06am
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