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Max volts through a t-bred b

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pwnt by pat

Member
Joined
Jun 16, 2003
Location
Cranberry Twp. PA
What is the maxium volts that can be run through the chip with any kind of cooling. That sandbox post has been more than helpful but it confuses me for the most part. AMD specs say that its 2.03 however in the database there are chips with higher voltage. I see most people don't run over 1.875 so what's concidered safe before frying the cpu?
 
truth be told the amount of volts u give will only be limited by your cooling

so keep giving it more until your temps get out of hand, then lower it back a bit

t-breds and bartons dont really die from too many volts
 
Tekko said:
you kidding me I'm running on 1.9v and with only a zalman 7000-a cu I get temp 11C above ambiant...

if you're running DUT3C, that's still just a little over the edge .. but certainly not recommended for long run.

DLT3C on the other hand, doesn't seem to get extra performance from excessive voltages (being I can run my 1700+ JIUHB@2300mhz on 1.75V, but it takes 1.875V to run it 2400mhz (and temp will go up like crazy - SK7 with SFII and direct blowhole))
 
pwnt by pat said:
What is the maxium volts that can be run through the chip with any kind of cooling. That sandbox post has been more than helpful but it confuses me for the most part. AMD specs say that its 2.03 however in the database there are chips with higher voltage. I see most people don't run over 1.875 so what's concidered safe before frying the cpu?

There is not a single number that can fit your question.


CPU voltage: from stock to max absolute, from efficient overclocking to diminishing return

1. For Tbred B/Barton, the default voltage ratings (stock voltage) are
- For mobile Barton, 1.45 V
- DLT3C 1.5 V
- DUT3C 1.6 V
- DKT3C 1.65 V
This is the default voltage rating AMD recommends to use.


2. The max absolute voltages that AMD put up are:
Quoted from AMD:
"The AMD Athlon XP processor model 8 should not be subjected to conditions exceeding the absolute ratings, as such conditions can adversely affect long-term reliability or result in functional damage."

- For DLT3C, e.g. 1700+ DLT3C
Vcc_core_dc_max = 1.5 + 0.05 = 1.55 V
The absolute rating for Vcore = 1.55 + 0.5 = 2.05 V

- For DUT3C, e.g. 1700+ DUT3C, 2100+
Vcc_core_dc_max = 1.6 + 0.05 = 1.65 V
The absolute rating for Vcore = 1.65 + 0.5 = 2.15 V

- For DKT3C and Barton, e.g. 2500+, 3200+
Vcc_core_dc_max = 1.65 + 0.05 = 1.70 V
The absolute rating for Vcore = 1.70 + 0.5 = 2.20 V
Ref:
Max Vcore for Tbred B and Barton (page 5)
How much voltage can be applied to a CPU (page 5)


3. For overclocking, the "efficient overclocking voltage" that gives the most overclocking frequency and keeps temperature below diminishing return is
- between 1.5 to 1.85 V for DLT3C and mobile Barton,
- between 1.6 to 1.95 V for DKT3C and desktop Barton
getting about 100 - 130 MHz per 100 mV.
Ref:
General rules on voltage and temperature for CPU overclocking (page 16)


4. If one needs to get the last MHz (last stable 100 MHz) from the CPU, then the CPU has to operate above the "efficient overclocking voltage" and below the "max absolute voltage" . The CPU would have to operate in the diminishing return regime in which every mV of voltage added to speed up the CPU frequency would be counter-acted by the heat increase which in turn slow down the CPU. The return of MHz from voltage is small (< 30 MHz per 100 mV, < 10 MHz / C) and is costly in term of cooling, power supply in this operating range.

This voltage range is recommended for benchmark testing and competition, and not necessary for 24/7 usage. If one has only a CPU to rely on, don't operate it constantly in this voltage range.
Ref:
Some numbers to determine max CPU overclocking frequency - Vcore vs temperature,
When do the CPU's slow down?
(page 13)
Explanation (page 13)


5. The effect of high voltage on CPU life expectancy is discussed in:

How to determine "highest" voltage and temperature for CPU overclocking (page 16)
Effect of high Vcore and electromigration on CPU failure time (page 15)
Effect of high Vcore and electromigration on expected failure time for Tbred B/Barton (page 15)
What is gate break-down voltage (page 16)


Related links:

Relationship of clock, die temperature and voltage (update)
- What is the active power of a CPU at frequency f and voltage V
- How to estimate CPU static and active power
- Effect of die temperature on CPU clock frequency at a given Vcore
(page 13)

Vcore vs processor frequency and cycle time (page 19)

Why frequency and voltage are important for overclocking performance (page 19)
 
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2. The max absolute voltages that AMD put up are:
Quoted from AMD:
"The AMD Athlon XP processor model 8 should not be subjected to conditions exceeding the absolute ratings, as such conditions can adversely affect long-term reliability or result in functional damage."

- For DLT3C, e.g. 1700+ DLT3C
Vcc_core_dc_max = 1.5 + 0.05 = 1.55 V
The absolute rating for Vcore = 1.55 + 0.5 = 2.05 V

- For DUT3C, e.g. 1700+ DUT3C, 2100+
Vcc_core_dc_max = 1.6 + 0.05 = 1.65 V
The absolute rating for Vcore = 1.65 + 0.5 = 2.15 V

- For DKT3C and Barton, e.g. 2500+, 3200+
Vcc_core_dc_max = 1.65 + 0.05 = 1.70 V
The absolute rating for Vcore = 1.70 + 0.5 = 2.20 V

There are some processor PRs which use the exact same core, but which have different stock Vcore voltages, with the faster chips having a higher stock Vcore.

Mobile Bartons are another example, where the core is identical to that of a desktop Barton, the only difference being the ability to run the same speed with a lower Vcore voltage, while maintaining stability. In this case, I don't think that the stock Vcore can be said to have any real affect on the 'maximum' Vcore you should give your processor.

Rather, I think that what you posted (see below quote) about diminishing overvolt returns is a better 'voltage limit' benchmark. When you get to the point of diminishing overclock gains per XXX mV it's time to stop overvolting. Maybe I'm just repeating what you said, but I feel that your 'maximum' amount of Vcore voltage is something that should be gathered through intuition, using your MHz:mV gains and load stable temperature as guidelines.

3. For overclocking, the "efficient overclocking voltage" that gives the most overclocking frequency and keeps temperature below diminishing return is
- between 1.5 to 1.85 V for DLT3C and mobile Barton,
- between 1.6 to 1.95 V for DKT3C and desktop Barton
getting about 100 - 130 MHz per 100 mV.
 
In my earlier post,

- the stock voltage is a manufacturer's specification.

- the absolute maximum voltage is also a manufacturer's specfication.

They are put up by manufacturer for technical and legal purposes, used by manufacturers and box makers for specification.

For overclocking, the actual maximum voltage depends on individual chips, and has to be determined individually, ..., how to determine
- the maximum voltage and frequency
- the efficient voltage and frequency
- the relationship and tradeoff between voltage, frequency, temperature, power, life expectancy, ...
are detailed in the post.



Relationship between stock voltage, highest stable voltage, power specification, overclockability, CPU internal characteristic, ... is a subject that should be addressed separately.
 
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1.85V with extreme aircooling .. beyond that, you need to watercool ..

You have got to be kidding me. I've run 1.9 for days with only a mediocre heatsink. Your max voltage all depends on your temps, (unless you have phase-change cooling.)
 
Quailane said:


You have got to be kidding me. I've run 1.9 for days with only a mediocre heatsink. Your max voltage all depends on your temps, (unless you have phase-change cooling.)

no, i'm not kidding you. he asked about T-bred B DLT3C which default voltage is 1.5V, and I don't feel comfortable looking at ~50'C load temp on my [email protected] (12x200) 1700+ JIUHB DLT3C.

with [email protected], I never go beyond 45'C on full load (both with ~25'C ambient temp). This is with SK-7 and SF2 @ 3500rpm 24/7 folding.

it's all about preferences.. for you, 50'C might still be an acceptable temp, but for me, it isn't
 
hitechjb1, you had all that posted in your sandbox 1700 ocing results/testing posts which I though was incredible, however maybe I wasn't clear enough or even too precise. While 2.05v is the AMD spec'd MAX for the chip, with proper cooling would it be safe to push the voltage higher or will it literally kill the cpu (I'm not going to push it that hard on water but I am thinking of going phase change soon)?
 
Okay, I re-read this section which I must have just skimmed over before:

This is what we call the diminishing return on CPU frequency. And eventually, around 1.95 - 2 V for Tbred B, 1700+ DLT3C, it will come to "stop" (due to heat, high current and system instability) even when more Vcore is put in, since the heat slows the chip down as electron mobility decreases as temperature increases. There is no more reason to increase Vcore anymore (even you don't kill the chip). For higher Vcore rated ones such as 2100+, Barton 2500+, that Vcore wall is around 2.05 - 2.2 V on air.

The above numbers are mainly for illustration, and they are roughly correct. But don't quote and use them for exact calculation.

If you use thermoelectric, phase change, .... exterme cooling, due to the lower die temperature, as mentioned above, the chips can run much faster and reach much higher frequency (e.g. 3+ GHz) at the same Vcore (compared to air/water) before the die reaching the higher temperature as cooled by air. E.g. at 1.95-2V 1700+ will run at 2.5-2.6 GHz on air at 50 C, but it will run at 3 - 3.2 GHz at -10 C.

It does not mean you can put much higher Vcore onto the chips at lower die temperature. Vcore is subjected to transistor leakage increase, gate breakdown constraints. They run faster is a combination of higher active power to substain the computation (both logical and electrical) and lower die temperature, not higher Vcore alone.

That makes more sense now. Thanks everyone I guess this is case closed.
 
pwnt by pat said:
Okay, I re-read this section which I must have just skimmed over before:



That makes more sense now. Thanks everyone I guess this is case closed.

Thanks for asking and bringing these questions up. I think the summary few post back on voltage is very basic for overclocking.

I wrote up all these technical stuffs during my learning and experimental process. I tried to answer these questions for myself and for others (when I saw some questions asked), and put them in the thread for later references.

That quote was written in last June 03, there are lots of technical content and even I reread it now, I feel refreshing and learn something from what I wrote, .... :)
 
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posted by felinusz

Maybe I'm just repeating what you said, but I feel that your 'maximum' amount of Vcore voltage is something that should be gathered through intuition, using your MHz:mV gains and load stable temperature as guidelines.

posted by hitechjb1

For overclocking, the actual maximum voltage depends on individual chips, and has to be determined individually.....

That's exactly what I'm trying to say. Forgive me if I took your direct quotation of AMD's frankly meaningless ratings too literally.
 
Dukemurmur said:
i get 38 load at 2.00.....i just tried it to c what i would get 4 temps


bringing back a dead thread? yes

38 load...assuming 20C ambient...(brrrr, way too cold for me) that's 18C.

18/~130w @ 2v=.13C/W

on air? me thinks not

you're looking at an error of +- 10C in motherboard reporting

mobos are only good for temps relative to themselves i.e. changing cooling on the board, observing results
 
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