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post #4 of (permalink) Old 04-28-2018, 11:42 AM - Thread Starter
⤷ αC
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1.425V is the max voltage per Stilt's interrogation of the Ryzen 7 2700x , I didn't pull it out of thin air:
The voltage command which the CPU sends to the VRM regulator via the SVI2 interface and the actual effective voltage were then recorded in various scenarios. In stock configuration the sustained maximum effective voltage during all-core stress allowed by FIT was =< 1.330V. Meanwhile, in single core workloads the sustained maximum was =< 1.425V. When the “FIT” parameters were adjusted by increasing the scalar value from the default 1x to the maximum allowed value of 10x, the maximum all-core voltage became 1.380V, while the maximum single core voltage increased to 1.480V. The recorded figures appear to fall very well in line with the seen and known behavior, frequency, power and thermal scaling wise.

The seen behavior suggests that the full silicon reliability can be maintained up to around 1.330V in all-core workloads (i.e. high current) and up to 1.425V in single core workloads (i.e. low current). Use of higher voltages is definitely possible (as FIT will allow up to 1.380V / 1.480V when scalar is increased by 10x), but it more than likely results in reduced silicon lifetime / reliability. By how much? Only the good folks at AMD who have access to the simulation data will know for sure.


Quote: Originally Posted by Robbert Hallock (AMD)
Hi, I work for AMD.
The CPU is programmed to use these voltages automatically. We know it's safe, because we designed it that way. The CPU cannot and does not use voltages that are unsafe for the silicon.
The key thing that people forget in these cases is time and temperature. Running 1.4V or 1.5V here and there is not a big deal, because the CPU will eventually back down according to its pre-programmed model. Or if you have great cooling, that also offsets the thermal effect of voltage. In either case, you're seeing momentary blips of voltage that are offset by the hours per day your CPU is probably doing nothing at all--at a very low voltage.
The average vcore for Ryzen over time is around 1.25V (give or take).
tl;dr: leave the CPU alone, let it do its thing, don't worry. We designed the CPU to do this.

1.425V is the recommended max voltage from Robert Hallock at AMD for Ryzen 1 too:


As far as manual overclocks:

If you run really high LLC (i.e. instead of medium or "HIGH" you run Turbo or Extreme) then obviously you need to account for that. If you are running full on AVX then you need to account for that. There's an inherent 0.02V V_Droop present with LLC set to HIGH. If you are on air then obviously you need to account for temperature also rather than just power and voltage, which means ~1.35V / ~170W is likely better. PB2 only kicks in below ~60°C to maximize reliability of the silicon.

You're fixating on voltage but if you pay attention to AMD's PB2 and XFR2 , the CPU will drop to 4.1GHz / ~1.2 to 1.3V only when AVX is being used to maintain the same power usage (power is not just based on voltage , gaming or idle at 1.4V is not the same as flogging the floating point units at 1.4V). If you turn on PBO the CPU will maintain around 4.175 - 4.225GHz.

There's three main variables used for the PB2 algorithm: current (EDC/TDC), power (PPT), and temperature.

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