agree but i have mentioned the Asus EPU turbo mode before and in prime 95 the temps jump to 44*c to 68-70*c within few sec's n after 5-10 mins it goes beyond 75. i have figuredout this all happens only in turbo mode n in asus EPU high performance mode the temps are 65-68*c.
for 1 hour prime 95 it was almost 80*c in real temp but we are taking abt the sudden jump of temp by 12-15*c, why is it so ?
Why the hell Asus EPU shows turbo mode on when i am running prime95 with all 4cores n 8threads ?
First of all, the following isn't a guide to OC, but either things you should already know before reading guides about OC.
The temp jump is normal. What you don't know is there are several power saving features from bios which reduce the amount of electricity going into the CPU. Some people are confused, or never knew how it works to begin with, but you can't change amount of electricity to drive the CPU.
CPU itself doesn't use much electricity to work. What requires electricity is the signal going into the CPU. In layman terms, when there are electricity, than CPU understood as 1, when there are no electricity, then it is 0. From 1 to 0 and back to 1 you have 1 cycle, and out of this cycle, half of the time it generates heat as it receives electricity as a signal which it reads it as 1.
If you have ever played with light switches by flickering it really fast, you probably know that the state of the lightbulb is neither on or off as the lightbulb requires time to charge up and discharge completely. In short, this event happens within CPU too, except that it happens really fast. 1 hz = 1 to 0 back to 1 onces a second, and your CPU flickers the power switch much faster than you can imagine. The speed of this act is also known as clock speed.
Imagine I am playing at the switch and you are looking at the light, will you be able to determine the speed I flicker the switch? You may say yes assuming whatever I do impact the light, but what you may not have consider is there are hundreds of people like me playing this in the same house. While it will be fun to play, you probably won't be able to determine that because every action anyone does with electricity have an impact to the lightbulb you are trying to use to determine my flickering speed. To make it more complicated, I will try to send a morse code through flickering the switch and you are to read the morse code send by me.
Whether you will be able to successfully receive the morse code I sent depends on the speed which I sent it with, the amount of interference you get, the charge/discharge time of the lightbulb, and the brightness of the lightbulb. The brightness of the lightbulb is important as you can determine the difference between 0 and 1 more easily in 2 ways. 1) the charge/discharge time decreases, and 2) the signal is more clear. While kids are busy inside sending messages with lightbulbs, heat is being generated. Each wire that connects the switch and lightbulbs itself generates heat.
If CPU is a room, then it looks pretty much like the room described above with millions of parts trying to do the send messages. To ensures that each and all of these messages are sent correctly, electricity going into this house must be very stable, and increasing the voltage means signals are more clear inside.
But what happens when no one is sending messages inside, well then CPU consumes less electricity, but there is always one kid who is playing, that kid is called the clock generator. However, when the activity inside the house it low, it means the interference is low, and therefore doesn't require the voltage needed as if millions of activities are going on, and therefore there are features in bios to reduce the voltage going into the house. Even if the voltage remind unchanged, the fact that there are no much activity going on, the amount of heat generated within the house decreases.
One 9volt battery can generate lots of heat, but that is when circuit is closed. If the circuit is open, then no heat is generated. This also happens within the CPU.
By default, Bios supplies about 1.2 volt into the CPU. At idle, since there are not much activity going on, and therefore not much heat is produced. Generally speaking, the heat from the CPU at idle is from the electricity needed to keep CPU running + the heat from the clock generator. At load, heat is produced based on the types of activities occured. The other way to predict heat generation is by measuring the amount of electricity consumed by CPU. At load, CPU consumed far more electricity then when it is idle.
Like tweakboy said, you can't stop heat from generating or reduce the amount it generates. You can however radiates the heat generated by off the CPU. When switching from idle to load, temperature will rise no matter what method you use to radiates the heat. The rate of heat trasfer is by itself a huge topic, but you don't need to know how does it work as long as it works. If contact between the heatsink and the integrated heatsink on the surface of the CPU is a problem, then the temperature will rocket even before your windows starts. That means BSoD. If it starts, then you run prime95 to ensure the signal is clear and the msgs sent within the CPU is indeed correct, else prime95 will show errors or BSoD.
The purpose of using Prime95 to test radate capability is to see if heat actually gets out of the case or circulating within the case. If you can run prime95 for without crashing for 1 minute, then the contact is fine, meaning the TIM is fine. If you can run it for 1 hour, then the Heatsink is up for the task of radiating heat off the CPU and that speed and voltage. If you want to know how much headroom you have for OC, the number you what to see is the "distance to TjMax", not temperature. If it is under 10, then you don't have alot of headroom. If it is under 20, then you can push the clock higher until voltage becomes a problem. If it is above 30, then you can play with the voltage gently.
In 1 minute of prime95, heat probably got from CPU to heatsink, you don't know if heat is being radiated of the heatsink. At around 30 minutes, temps should be raising very slowly. If temp increases after that, then it means the ambient temperature around the heatsink increased. After 1 hour, if temp increases, then the ambient temperature within the case probably increased. After several hours, the room temp increases.
If torturing your PC isn't the point of all these tests, 1-2 hour of prime95 is enough to ensure stability of the PC. In your case, everything work as intended.
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