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Is 1.95 volts too much ?

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fsarfino

Member
Joined
Aug 9, 2003
Location
Naperville IL
I'm running 1.95v on my 2500 barton (unlocked) this was the only way for me to get 220 fsb on my NF7-S ver 2.0.

Right now I have a pretty good water cooling setup and I'm reading 52c at full load off of the thermal diode. But I have heard that these readings are not accurate.

What ya think.

Thanks
 
fsarfino said:
I'm running 1.95v on my 2500 barton (unlocked) this was the only way for me to get 220 fsb on my NF7-S ver 2.0.

Right now I have a pretty good water cooling setup and I'm reading 52c at full load off of the thermal diode. But I have heard that these readings are not accurate.

What ya think.

Thanks

#1 Yes its fine..... AMD reccomends that the voltage stays below 2.1v to function properly. They consider that the maximum safe v-core for desktop Bartons.

#2 It depends on what BIOS you are using. D10 was horribly off, ranging between 10-15c* high. D21 and higher read dead on.
 
Re: Re: Is 1.95 volts too much ?

Sentential said:


#1 Yes its fine..... AMD reccomends that the voltage stays below 2.1v to function properly. They consider that the maximum safe v-core for desktop Bartons.


Sentential, do you happen do have a tech-doc, link or something that states this?
 
Re: Re: Is 1.95 volts too much ?

Sentential said:


#1 Yes its fine..... AMD reccomends that the voltage stays below 2.1v to function properly. They consider that the maximum safe v-core for desktop Bartons.

#2 It depends on what BIOS you are using. D10 was horribly off, ranging between 10-15c* high. D21 and higher read dead on.

So I could go to 2.1 volts then ? So what is considered too high of a temp to run at ?

Yes I have Tic Tac's d23 subzero bios installed so I can assume that the temp's are correct then.

Thanks for the info Sentential
 
I really wish I could find that tech document:( ...but yes that was pulled from an official AMD sheet.

Ironically the voltages were different per core and type... I knew I shoulda made a record of that.
 
Re: Re: Re: Is 1.95 volts too much ?

fsarfino said:


So I could go to 2.1 volts then ? So what is considered too high of a temp to run at ?

Yes I have Tic Tac's d23 subzero bios installed so I can assume that the temp's are correct then.

Thanks for the info Sentential

i think the temp was very very slightly higher in 23 on my board. i use a max zone of 55c diode for ~1.9 core. but, as u go higher, the max should become lower.
 
Found it:

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)
- from a post here from "1700+ Overclocking Sandbox"

Soooooooo.... for the 35w 2400+, the max safe voltage is 1.9v
 
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Sentential said:
Found it:

- from a post here from "1700+ Overclocking Sandbox"

Soooooooo.... for the 35w 2400+, the max safe voltage is 1.9v

dunno what is safe or not safe, ha.. ill let u know if anything blows up/burns in the longrun, hehe.

i wont dare go above 1.93 or so on air.. no matter how good the air is or how low the temp is.. but thats me..

edit: "i wont dare go above 1.93 or so on air" for 24/7 operation.
 
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Thanks for all the info. I think I might back down on it a little until I install my temp. probes on the cpu and the NB. Hopefully I'll have the time to do it tonight after work :)
 
What voltage to run depends on many factors, your objective, how long you want to keep the CPU, whether you want to run the CPU to get the last MHz or run the CPU cost effectively, .... For details, here is some detailed explanation:

hitechjb1 said:
There is NO clear Yes or No answer to predict "life expectancy" and "safe overclocking voltage" of a particular CPU based on voltage and temperature. For a given CPU type, they follow certain statistical behavior.

The inverse relationship between frequency and temperature will naturally determine the max voltage and frequency for a given CPU and cooling setup. If overclocking is done properly, such voltage and temperature should be below the max absolute temperature and voltage of a given CPU specifcation (at least true for Tbred/Barton).

For example, assuming nominal voltage is 1.5 V.

Running it constantly at 1.8 V is 20% over nominal and running it at 1.95 V is 30% over nominal voltage.

From electromigration analysis, keeping temperature roughly constant (by cooling), overvoltage from 20% to 30% decreases CPU failure time (life expectancy) by about 10% (failure time reduced from 69% to 59%)

For Tbred B/Barton/Mobile Barton, the frequency gain between 1.8 V to 1.95 V is about 75-100 MHz at 2300-2500 MHz level, it is stating to operate in the diminishing return regime, getting only 75-100 MHz from 150 mV Vcore increase. The gain in overclocking frequency is about 3 - 4%.

The most effective, cost effective overclocking voltage for Tbred/Barton is between 1.5 - 1.9 V, beyond which overclocking is very costly in terms of power supply and cooling with diminishing frequency gain.

So it is a tradefoff between frequency, voltage and life expectancy.

Going from 1.8 V to 1.95 V, one would get 3 - 4% increase in overclocking frequency at the expense of an additional 10% reduction in CPU life expectancy (statisitically).

But then a different person uses a CPU differently and have different objective, some expect to use it for 6 months, 1 year, some for 3 year, ..., some want to squeeze the last MHz for competition and satifaction, so one has to make his/her own judgement and tradeoff, ...

This post discusses this subject in details:

CPU voltage: from stock to max absolute, from efficient overclocking to diminishing return (page 19)
 
Unforutnatly I dont think those figures work for a Mobile Barton...unless you have corrected for that already.

On that note... where did you find that info from hitechjb1?
 
Sentential said:
Unforutnatly I dont think those figures work for a Mobile Barton...unless you have corrected for that already.

On that note... where did you find that info from hitechjb1?

To calculate the max absolute voltage, first I obtained some raw numbers from the AMD tech doc for model 8 (Tbred) and 10 (Barton), then have to do some calculation based on these raw numbers, ... The details are shown in the posts from the links on max voltage ....

For mobile Barton which the model 8 and 10 tech doc do not cover, but since mobile Barton is a derivative from Tbread B + Barton, so its max absolute voltage should resemble that of Tbred B 1700+ DLT3C.


But anyway, one should NOT take the max absolute voltage as so rigid, black and white, under which is completely OK and above which is completely forbidden. One should NOT base a computer design or overclocking on the "absoulte max voltage" number.

Every CPU/chip is different, even the a large sample of them follow certain (normal) distribution. Even at stock voltage, there can be a very small failure rate.

The inverse relationship between frequency and temperature will naturally determine the max voltage and frequency for a given CPU and cooling setup. If overclocking is done properly, such voltage and temperature should be below the max absolute temperature and voltage of a given CPU specifcation (at least true for Tbred/Barton).

From the posts (listed below) on voltage that I wrote, regardless whether it is totally agreed upon, at least we should see and appreciate that there are many aspect of voltage (whether it is operated under stock, most effective, diminishing return, max regime, ...), and voltage, temperature, frequency, stability, ... in overclocking/computer design as a complex, multiple dimensional process. Especially at 20%, 30% above rated specification, there is NO simple, sinlge number of voltage, temperature, ... that can fit all situation.

CPU voltage: from stock to max absolute, from efficient overclocking to diminishing return (page 19)
 
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hitechjb1 - you are the man! :D

I would take n=3 (99.97% of the stated chips) to define "absolute" value.

I've noticed that the Stable_Mhz = F(Voltage) funcion behaves somehow like
F = - (X)/(Voltage) +Max_mhz,
where Max_Mhz is maximum stable Mhz that could be achieved by the chip, no matter the voltage you add.

My point is when you reach the point you need to raize the voltage above 1.9V ( which is safe) you won't yield any significant Mhz gain , but only shorten your CPU life.
 
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