Live Overclock, is voltage drop normal?

Rolando_d · Apr 2, 2014

Hey guys, quick question, Im overclocking my FX 8320 processor and its only at 3.9Ghz from stock 3.5Ghz and even though I have Core Voltage set to 1.32V when I run prime95 it drops to 1.28V and fluctuates between that and 1.2V

When I raised voltage by .025 to 1.35V for core voltage, I then saw voltage during test hold at 1.232V but drop sometimes down to 1.15V. Is this normal under stress?

FX 8320 8 Core Processor
EVGA GTX 760 GPU
8Gb Gskill DDR3 Ram
GA-970a-ud3 Mobo
600W PSU
120Gb Samsung EVO SSD
500Gb 7200rpm barracuda
Hyper 212 EVO CPU Cooling Fan

Textfield · Apr 7, 2014

Rolando_d :

Increasing voltage doesn't give you an overclock per se. You have to increase the clock speed multiplier as well to bring up the GHz.

3.9GHz is actually within your "stock" clock speed. AMD implements a setup in the 8320 whereby its clock speed can hit up to 4.0 GHz given that it detects its properly cooled (which the 212 EVO should be able to do fine) without any actual overclocking or overvolting. Increasing the voltage is unnecessary for hitting the speeds you're currently hitting.

It's likely only hitting 3.9 because it scales back when all 8 cores are in use.

To overclock, you simply have to increase the multiplier. A lot of the time CPUs can hit higher multipliers without any increase in voltage, because factory settings are often fairly conservative. It's only if you want to push the CPU even further that you need to think about more voltage.

Your core voltage is less than what you set it at because your CPU is detecting it doesn't need that much voltage to run at that speed.

And remember that temps stay reasonable.

mr195 · Jun 8, 2014

From my experience, voltage drops occur from the Load Line Calibration setting of your motherboard. I have the gigabyte 990fxa ud3, and I get voltage drops unless I turn it off. But when I turn it off, it over-volts and crashes.

Pinhedd · Jun 8, 2014

Rolando_d :

Voltage dropping under load (commonly called vdroop or Load Line Calibration) is not only normal, it is specified by the manufacturer.

The reason for this is in the way power is delivered. Power is delivered to the CPU from a number of voltage regulators located nearby. These regulators are programmable buck converters. A buck converter is a DC-DC step down transformer. The ones on PCs take in a nominally 12 volt supply and spit out a programmable voltage, typically between 1 volt and 1.5 volts.

The mechanism of the DC to DC conversion operates by modulating a power transistor with a variable duty cycle high frequency square wave to charge a loading capacitor. This is remarkably similar to the way fan speed is controlled, increasing the duty cycle increases the rate of rotation of the fan. The modulation of the duty cycle is controlled by a feedback loop that measures the voltage across the loading capacitor and comparing it to the programmed output voltage. If the voltage rises above the programmed voltage, the duty decreases; if the voltage drops below the programmed voltage, the duty increases. As such, it is constantly adjusting to the power needs of the CPU at a rate typically on the order of several hundred thousand times per second.

If the power needs of the CPU change very suddenly at the wrong moment the feedback loop may not be able to adjust the modulation until the charging circuitry has already charged the loading capacitor well above the target voltage. Motherboards with high quality power circuitry operate the modulation at a higher rate, use more power delivery phases, or use larger loading capacitors, and are thus less prone to this problem. Most of these motherboards contain a firmware setting to adjust the Vdroop.

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Live Overclock, is voltage drop normal?

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