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Old 05-07-03, 08:11 PM Thread Starter   #1
Footba_SWAT5420
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vcore temp increases


when you guys bump up your vcore how much did your temp increase. im getting an 8rga+ and 2100tbred. im pretty much a noob to overclcoknig the CPU. i know how to do it but dont have the money to do it yet im going to have an slk900 w/ tornado cooling it so i dotn think i need to be too conserned but it would help alot if you posted your tmeps after the change.
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Old 05-07-03, 08:40 PM   #2
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I can't really remember how much temps increased with each tenth of a volt. Just bump it up a little and see what happens, noone will have the same results. Trial and error is about the only way to see whats gonna work...

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Old 05-07-03, 09:08 PM   #3
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When I bumped my vcore from 1.8 to 1.85 for the current OC that I have, my full load temps went from 47C to 57C...

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Old 05-07-03, 09:15 PM   #4
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Relationship of clock, die temperature and Vcore

As far as Vcore, clock and die temperatue relationship, a chip (CPU) can be modeled as a capacitor C and a resistor R in parallel driven by Vcore. C models the useful active power to substain the computation by charging and discharging 100 millions of internal capacitors (from coupling between transistors, wires and silicon subtrate). R models the wasted leakage power through the internal current paths through the dozens millions of transistors.

If the die temp is kept low enough, in theory, todays XP and P4 can be clocked as high as 3 GHz, 4 GHz. The power (the C component) going into the chip to run the clock at a frequency f and Vcore V is given by

P_active = C V^2 f

And this can go on to 3-4 GHz if the die is kept below certain temp. Most of the power are used to power the clock faster as Vcore is increased.

But in reality, for any cooling used, air, water, vapor, liquid nitrogen, ..., the die temperature will eventually increase as Vcore increases due to leakage current which heats up the chip. Though at a different rate depends on what cooling is used. The leakage current is small at low temp, and increases with temp increases and also at a faster rate as temp increases. The power that heats up the chip (the R component) is given by

P_leak = V^2 / R

From my experiment with the TB B 1700+ DLT3C, when die temp reaches around 40C, the chip leakage current begins to increase at a faster pace, and heats up the chip more. Once this starts, any Vcore increase will split between powering faster clock, but also in heating up the chip. The exact Vcore when this occurs varies from chip to chip (100-200 mV difference), it depends on the "gene" how a particular CPU was born.

P = P_active + P_leak = CV^2 f + V^2 / R

After passing that temp threshold, the portion P_leak going into heating the chip (the R component) will become larger and larger, as Vcore is increased. In other word, the useful P_active to power the chip faster (the C component) will eventually become very very small. And the chip is just being heat up and cannot be clocked faster any more.


If better cooling than air such as vapor, liquid nitrogen are used, the chip may reach that temperature threshold (40C) at a much higher Vcore. That is, more power can be used to power the P_active portion to a much higher clock frequency before the CPU reaches that temperature threshold of high "run away" leakage. But still, the leakage current will still increase, but at a much slower pace due to lower die temperature, until which the die temp reaches, say 40C again, but at a much higher Vcore for a much higher clock frequency (hopefully 3-4 GHz). And at that point, overclocking will still begin to hit a wall like air cooling then.

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Last edited by hitechjb1; 05-07-03 at 09:35 PM.
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Old 05-07-03, 09:24 PM   #5
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Holy crap, hitechjb! where do you find this stuff?

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Old 05-07-03, 09:28 PM   #6
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hey hitechjb1, nice stuff you got there, very well

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Old 05-07-03, 09:32 PM   #7
hitechjb1
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Quote:
Originally posted by altec
Holy crap, hitechjb! where do you find this stuff?
From the law of physics, and when I write it down to explain, it also helps me to understand better.

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- ASUS A7N8X DLX, Tbred B 1700+ 0310 XPMW 2.56 GHz (205x12.5) 1.94 V, max at 2.6 GHz, SLK-800U + TT SFII, 48/40 28/26 C, 512MB 3500 C2 2-3-2-5 (retired)
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Old 05-07-03, 09:35 PM   #8
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Quote:
Originally posted by hitechjb1
it also helps me to understand better.
lol

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Old 05-08-03, 03:29 PM Thread Starter   #9
Footba_SWAT5420
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um yea i dont tkae physics till next year so ill come look at this then
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Old 05-08-03, 05:02 PM   #10
hitechjb1
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Quote:
Originally posted by Footba_SWAT5420
um yea i dont tkae physics till next year so ill come look at this then
You have a good start.

When you know more about physics and math, you'll do oc and many other things better, ...

From you sig, you have a 2100+ coming. It is good, since I think the 2100+ is even more stable at high Vcore (in case you overclock), and can stand a little better at higher temperature and a little bit less leaky (less sensitive to temperature) compared to 1700+. It is because its transistors are a little bit longer in length, I suspect.

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Overclocking sandbox: Tbred B DLT3C and beyond
- DFI LP UT NF4 Ultra-D, Opteron 165 CCBBE 0610 DPMW 3.00 GHz, highest clock 3.30 GHz, XP-90, G. Skill 4800 2 x 512 MB, X800Pro (Winchester 0447 CBBHD 2.83 GHz 314x9 1.52V)
- ABIT NF7-S rev 2.0, Mobile Barton 2600+ IQYHA 0351 MPMW 2.71 GHz (225x12), 18/37 C, 1.89 V, SLK-947U 80mm Tornado (w/ fan control), 512 MB x 2 3500 C2 2-3-2-5, 9500 np -> 9700 np 360/311
- ASUS A7N8X DLX, Tbred B 1700+ 0310 XPMW 2.56 GHz (205x12.5) 1.94 V, max at 2.6 GHz, SLK-800U + TT SFII, 48/40 28/26 C, 512MB 3500 C2 2-3-2-5 (retired)
- Intel 8088 4.77 MHz 8bit CPU, 64KB memory, 1 MB HD, 5 1/4" floppy drive, DOS, 200 bps modem, 80x25 char display
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