Snipe, im with you there, programming just doesnt seem to work whenever i dot i!
This is great to hear though, I had heard that the lower temps allow greater frequencies at the same voltages (and I have hoped, considering the highest on air I have got with my e7300 is in my sig, and that took 1.7v!)
And so I was worried that there wasnt much point in using DICE with this cpu, (would be my first time)
However, reading stuff like this makes me realise that not only would I be able to use 1.8, 1.9 volts without it being too hot, due to the lack of heat, I will be able to get higher frequences at the volts I have already tried, (must admit, have tried 1.8v!)
George
Last edited by GeorgeStorm; 01-27-2009 at 11:01 AM.
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So far with Phenom II X4 it looks like the colder the better. We saw -242 Celsius measured from base of F1 EE copper container (1 - 2 mm from bottom surface):
and around -230 measured from AMD Pete Hardman's container where thermal sensor is milled right in the middle of bottom surface so it is basically touching CPU heatspreader. Under load temperature was -225 Celsius:
Since the system was running just fine at these temperatures I wouldn't be surprised if Phenom II X4 could work at -250 and -260C range. Next step is to design more sophisticated solution to use liquid helium to cool down the CPU to even lower temperatures than we achieved in Las Vegas.
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Favourite game: 3DMark
Work: Muropaketti.com - Finnish hardware site
Views and opinions about IT industry: Twitter: sampsa_kurri
This explains a whole lot thanks! Always wondered why temperatues mattered so much when clocking, I only knew it did matter!
Nice discussion , going to XOC Q&A section and sticky
it seems you gave the answers, yes two main thing we have for overclocking,
1.increasing voltage
2.cooling down
1. is definetly for keeping 1-0 level when you increase clock frequency, and 2. is for higher electrical conductivity of semiconductors under cold which allows transistors to switch faster with lower potential difference.
but if we came to coldbug again, that is usually complicated,but here my theory on this is that;
yes, lower temp means higher electrical conductivity but that is the case for semiconductors only, if we look at metals or other materials side it is reverse, when you heat you got higher conductivity, so what i want to come with is that somehow metal molecular side of the chip may cause coldbug since its conductivy is effected by extreme cold. yea this is theory, some may prove or not by giving how the metal parts of chip acts
Gautum,
How does th increase of voltage help reduce the high low delay, and therefore allow higher clockspeeds, is it just because more volts will cause the transistors to switch more quickly?
My flickr - My blog it'sfilmnotmovie
There are two basic reasons why increased voltage lets the caps get charged faster and the transistors switch quicker. First of all, the increased supply voltage increases the drive current across the transistor, so it charges it's own output cap quicker.
Secondly, all voltages are increased, so the input voltage is increased as well. In my crappy diagram I idealized the input into a perfect square pulse, but in reality, the input is coming from another transistor's output itself, so the input also rises and falls for some given period of time, like below, so increasing the input voltage at the gate allows the transistor to start switching faster as well.
but is it really the voltage increase, or the current increase that allows faster switching?
Or is the voltage a sneaky way of bypassing current limits?
Well higher voltage comes back to drive strength.
There are minimum setup and hold times for stable clock switching.
There are "on" and "off" thresholds for a clock signal. E.g.... 67% (or more) of max amplitude is "on" for the rising clock and 70% of max amplitude is "off" for the falling clock
Higher voltage to the clock gives it a higher maximum amplitude.
rising and falling edge clock transitions are not vertical lines with respect to time- they have a slight slope- a very steep one, but a slope all the same. They take a finite time to change
Making the max amplitude bigger but keeping the low-high transition time the same means that the signal will pass the "on" threshold faster and will be a more stable valid clock.
There is also a mean time to metastability which has a temperature dependence, as well as reliance on specific device constants. Metastability drawn as a clock means the signal meets itself coming back and cant decide if its on or off.....so falls over.
I should add some diagrams to show this but im too tired... if no-one beats me to it, I might give it a shot tomorrow.
It would be interesting to design a chip that would not compare on and off with set levels, but by the change from the previous step, this could possibly add more overclocking head room, although you would have to set the change threshold to a specific level because I would imagine that it would be unreliable after a point.
As far as parasitic capacitances need charging, increasing one or the other while holding the other constant would make it happen quicker.
From the standpoint of the transistor, voltage in fact is at first directly proportional, and then a square factor for the drive current as it changes operation modes. You can check this out if you want, slides 5-8 are relevant.
Yeah, I understand that, I guess my question would be more directed at what point is it current, rather than voltage, that is needed, but then, I suppose that would depend on the resistance of the transistor. Cooling the cpu lowers the resistance, and by my mind, by better aligning the crystal's lattice, allowing for higher clocks at the same voltage.
Due to variations in the lattice structure, the current, and voltage, required for a specifc clock speed changes from chip to chip.
.
So who's go the transistors that require less current to run...AMD or Intel? Given AMD specs Phemon 940 .85-1.5v, I would think AMD...but I dunno, becuase the work they do is slightly different.
Last edited by cadaveca; 01-28-2009 at 05:20 PM.
What if instead of a defined voltage for "on" and a defined voltage for "off, the switch would be based on the change in voltage between each cycle, this could possibly allow for "looser" cycles and improve clockability.
That's known as sense amplification and is basically necessary in RAM to be practical.
Reducing temperature has different effects on the conductivity of different materials in the CPU. It will increase the conductivity of the copper and silicon, but decrease the conductivity of the silicon dioxide dielectric. The latter reduces current leakage and helps the system tolerate higher voltage.
When will new semiconduter materials be required? In other words, are we at the boundaries yet of silicon? It seems as Guatam explained it, there will eventually be a limit of how fast the CMOS switches between PMOS and NMOS generating the 1-0 signal neccessary. Yet with AMD recently pushing past 7ghz on "old" technology, it seems like it is more in how effecient the rest of the system is and not neccessarily all on the switching of the signal inside the processor itself?
What did Intel pull off with SB that allowed the discharge of electron to happen quicker at "normal" operating temperature? I.E. 5ghz possible without increasing electron conductivity greatly through temperature?
Originally Posted by Sister
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