To begin, it is best to explain exactly what overvoltage accomplishes, and how voltage works in the first place. If you want to get right into the theoretical overclocking side of things, and aren%u2019t curious at all about how it all works, feel free to skip this very lengthy bit %u2013 or come back to it later on.
Overvolting does not increase overclocking potential by giving our hardware "more juice" or "more fuel". It increases overclocking potential by altering signal strength.
Our computers use a language of 1s and 0s %u2013 the binary language of computer processes. Physically speaking, these 1s and 0s occur through voltage highs and voltage lows, two signals representing a 0 (voltage low), and a 1 (voltage high). 0V typically represents voltage low, referred to as VSS. Voltage high is typically referred to as VCC, VDD, or VCORE, and is a variable voltage, dependant on the specific piece of hardware in question, and the transistor type used within that hardware (For example, a 90nm Athlon64 3200+ has a stock VCORE of 1.5V. A 90nm intel 540J 3200 MHz Pentium 4 has a stock VCORE of 1.4V).
So, 0V (voltage low, or VSS) is treated as a 0. A voltage close to Voltage high (VCC/VDD/VCORE), is treated as a 1. Our transistor-based hardware is essentially a massive grid of constantly switching voltages, representing logic 1s and logic 0s %u2013 the binary language in a nutshell.
The point of importance to us as overclockers here, is the "If our processor sees a voltage close to Voltage high (VCC/VDD/VCORE), it treats it as a 1." bit. Because of various resistances, our hardware%u2019s transistors must have a tolerance for voltage high %u2013 the exact value of VCORE/VDD/VCC is rarely seen. From now on, I am going to refer to voltage high as VCORE, for simplicity%u2019s sake.
Lets use an example to explain this tolerance, where we have a transistor voltage high (VCORE) of 1.4V, and a tolerance of ~5%. If the stock VCORE is 1.4V, and a signal of ~1.35V is seen, it will be regarded as a 1 (the tolerance allows for a ~5% loss of voltage high %u2013 or a minimum of ~1.33V). The really interesting bit for us, is that when the tolerance threshold is exceeded, our hardware starts to mess up. In our little example (with a ~5% tolerance, and a 1.4V transistor), if a voltage of 1.25V were to be seen, it would likely be regarded as a 0 instead of the 1 it was supposed to be %u2013 tolerance has been exceeded. Our signal strength (the signal itself being the voltage) has weakened enough that the tolerance is exceeded, and our hardware makes a mistake %u2013 stability is compromised! Most modern transistors have a tolerance ranging from ~2% through ~10%.
Overclocking our hardware can throw our voltage signals out of tolerance, and cause problems when a 1 (VCORE, voltage high) is mistaken for a 0 (VSS, voltage low).
The best way to explain how this happens when we overclock, through use of imagery, is through the use of a runner. This runner is running back and forth on a 100 foot track. He can either be at one end of the track (Voltage high - VCORE), or at the other end of the track (Voltage low - VSS). But, our runner cannot immediately switch from one end of the track to the other (and likewise, our VSS cannot switch to VCORE instantly). There is a transitional period where our runner is partway between the different ends of the track. The runner is rapidly running from one end of the track to the other (this is the same as our signal switching from VSS to VCORE), and although he is quite quick, there is still a delay between each end of the track (there is also a delay when our voltage signal switches from VSS to VCORE).
The rate at which he is expected to get from one end of the track to the other in ten minutes is our frequency, similar to the frequency at which our hardware operates. At a "stock", un-overclocked frequency, the runner is easily capable of making it to either end of the track in time. The frequency of %u2018on%u2019/%u2019off%u2019 signals %u2013 voltage high and voltage low signals - representing 1s and 0s, is how fast our hardware can %u2018think%u2019 and process. When we overclock, we increase the frequency at which the runner needs to make it from one end of the track to the other (we increase the frequency at which our signal needs to switch from VSS to VCORE), and we shorten the amount of transitionary time allowed for the runner to make it to the other end of the track (when we overclock the frequency, we shorten the amount of transition time allowed for VSS to switch to VCORE).
We increase the frequency (overclocking), and we get to the point where it is impossible for our runner to completely make it to each end of the track in the amount of transition time that he is given. The runner is simply not given enough time to make transit from one end of the track to the other, given the extreme frequency rate expected of him. Now our transistor tolerance comes in. The runner only really needs to make it to the 95 foot mark on the track in order for his run to be registered as a 1 (A 5% tolerance). Increasing the frequency slightly (and as such shortening the transition time the runner is given), the runner is still able to make it to the 95 foot mark, before he has to head back towards the other end of the track in order to meet his frequency schedule. But when we increase the frequency too much, the runner cannot even make it to the 95 foot mark before he has to turn back towards the other end of the track to meet his frequency schedule (VSS cannot switch to VCORE completely within the transitionary time allowed). Our runner only makes it to, say, the 90 foot mark, and is no longer within the tolerance %u2013 his run is counted as a 0 instead of as the 1 it is supposed to be. This represents an overclocked an unstable processor.
In our transistor based hardware, it takes time for the VSS voltage low (0V) to switch to our VCORE voltage high. When we overclock our frequency, we shorten the length of time available for that transition to take place. When there is inadequate time for VSS to change to VCORE, the signal (the signal itself being voltage) doesn%u2019t make it all the way to VCORE %u2013 at a certain point our transistor%u2019s voltage high signal tolerance is exceeded, and the VCORE signal is not strong enough to be registered as a 1 anymore. Instability occurs as a result %u2013 our 1s are being mistaken for 0s, and the computer cannot make sense of it.
Overvolting can alleviate this problem. The issue lies in the amount of time that it takes for the signal to change from VSS to VCORE %u2013 the signal can%u2019t switch quickly enough to reach a strength recognizeable as a voltage high (VCORE) by our transistors. When we increase our voltage high value (overvolting), we force the signal/voltage to reach a higher voltage high, but in the same amount of time as before. We stretch out the %u2018range of motion%u2019 (the difference between VSS and VCORE), but we leave the transition time alone. The result is that it takes considerably less time for the signal to switch from VSS to a VCORE that is within transistor tolerance %u2013 this accommodates our faster switching frequency, and keeps our overclocked signal switching frequency strong (stable) and within transistor tolerance.
Lets go back to our runners. Now we have two runners, and shall compare them in order to explain how overvolting alleviates the problem of inadequate signal transition time %u2013 which directly leads to instability. In this example, the measurement %u2018feet%u2019 represents voltage signal strength, and the measurement %u2018time%u2019 represents the transition period between VSS and VCORE. Runner #1 can run 100 feet in 20 seconds (Stock VCORE), Runner #2 can run 110 feet in 20 seconds (VCORE overvolted by 10%). Runner #1 can run 5 feet per second. Runner #2 can run 5.5 feet per second. Our overvolted signal switches slightly faster than our stock signal, in the same time period, just as runner #2 can run further in the same time period. Please keep in mind that this is a simple example for explanation, and that signal switching speed is not so linear as "10% overvolt=10% signal switching speed increase".
At a stock frequency, we have 20 seconds to get within transistor tolerance, say it%u2019s 5%, or 95 feet. Both runners make it. Now we overclock our frequency, and shorten the amount of time in which the runners have to get within our transistor tolerance of 95 feet. We increase the frequency, and shorten the transition time to 18 seconds. Runner #2, running at 5.5 feet per second, makes it to the 99 foot mark in 18 seconds, he is within tolerance, and his run is correctly counted as a 1. Runner #1 isn%u2019t fast enough. He makes it to the 90 foot mark in 18 seconds, and is not within the tolerance. Runner #1%u2019s run is incorrectly counted as a 0, and we have instability. In this manner, increasing signal switching speed to directly increase signal strength, overvolting allow us to increase our frequency (overclocking), without compromising stability when we also shorten the signal switching transition period.
That about sums up how voltage works in our transistor based hardware, as well as the effect that overvoltage has on increasing our hardware%u2019s stable overclock potential.
Facebook
Twitter
Instagram