Aparently the A64 dont care about voltage.

CandymanCan said:

Im trying to figure out why my cpu is stuck @ 2500mhz right now, i can get 2550-2600-2650, all the way up to a 3130mhz post, but any amount of voltage like 1.6-1.7-1.8-1.85v doesnt seem to matter for the cpu. Even cooling doesnt seem to matter also.

I know i can get 2600mhz stable if i keep messing with the system but i think its wierd how 2510mhz will work with just 1.6v, but anything higher then 2500 like 2515mhz doesnt work even with 1.7-1.8-1.85v.


Wierd.

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Originally posted by hitechjb1
At a given temperature, the higher the Vcore is, the smaller the delay in a logic gate for a given circuit, hence the smaller the cycle time T can be, or the higher the clock frequency f can be. As seen above, to the first order, without the contraint of heat, the maximum clock frequency varies somewhere, from with the square root of voltage to linearly with voltage. This is the good news - higher voltage can get it to run faster.

The bad news is, the higher the Vcore, the active power (C Vcore^2 f) and leakage power (Vcore^2/R) would also increase, where C and R are the equivalent capacitance and resistance to model the chip power dissipation. Up to a point, the slow down and instability effects due heat and temperature increase outpace the gain in clock speed, and diminishing return occurs. There is a delicate balance between voltage and temperature at optimal overclocking.

To summarize, Vcore improves the maximum CPU clock frequency (fmax) for a given CPU chip with same architecture and circuit under certain operating condition of temperature. So with sufficient voltage, within a (very) short period of time (1/1000 – few seconds), the CPU should be able to operate at such maximum frequency (fmax), before temperature begins to rise, leading to instability unless sufficient cooling is incorporated to limit any adverse effect of temperature on electron mobility, higher leakage current and instability perturbation on electronic components.

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Originally posted by hitechjb1
...
The higher the voltage and frequency, the higher the power and the higher the temperature. Such active power will increase the CPU to certain temperature under certain load for a given cooling.

Since carrier mobility decreases as temperature increase beyond certain temperature due to lattice scattering, transistor switching slow down as temperature increases. So the frequency f of a CPU varies inversely with the temperature, or df / f = - k dt, mathematically, where f is frequency, t is temperature, and k is a constant.

The balancing of these two opposing actions, or the intersection of the voltage-frequency curve and the temperature-frequency curve of a CPU characteristic naturally determines the final stable voltage/frequency/temperature operating point. If overclocking is done properly, the maximal overclocking should settle naturally at certain frequency, voltage and temperature, as desribed above, below the maximum absolute rating of voltage and temperature (as seen from Tbred/Barton, ...). A perceived stable voltage and temperature setting may not be necessary after all, if the voltage, temperature, frequency variations are monitored properly and adjusted incrementally.

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