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what is the absolute highest Vcore i should go to.

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Aristotle-IV

Registered
Joined
Sep 9, 2003
With an NF7-s and a 3000(333) version.

I have good cooling at full load at 1.85 in around 46c.

What is the highest i should set my Vcore to?
 

Hughhefner

Playboy Wannabee
Joined
Feb 2, 2003
Location
The old Playboy Mansion in Chicago
What is the stepping of your CPU, if you have the LOWER voltage DLT3C'slike I have you shouldn't go as high as some others like DUT. The difference is in the amperage at a given clock speed.

For my LOW voltage CPU's I am able to run at 2400-2450 at 1.825-1.85V and still keep temps at 123-125 F at load.
 

Carmine_Paterno

Member
Joined
Dec 21, 2000
I don't recommend keeping that expensive chip (I have one too see sig) over 2v for very long. Testing I dont see a problem with, but not for constant use. Check your temps also.
 

Hughhefner

Playboy Wannabee
Joined
Feb 2, 2003
Location
The old Playboy Mansion in Chicago
Sorry I just realized you had a BARTON not a tbred.
Just watch your temps, 46 is still ok, but I don't feel comfortable going over 50-52 with such an expensive chip.

My $65 Tbred b's aren't a big loss so be careful. 1.9V should be fine with GOOD cooling. My previous Barton would do 3200 speed at stock but on hit 2350mhz with 1.9V, man was it HOT so I kicked it down to run 200X11.5 at 1.875V and had 125F temps
 
OP
A

Aristotle-IV

Registered
Joined
Sep 9, 2003
Well I am doing 206 x 11.5 at 1.825.

2.38 Ghz almost 2.4ghz, my FSb dont seem to want to go high enough for me to go to an 11 multi.

My timings are 5-2-2-2 so that is crisp as well.

ill try to get a few more mhz out of it but i dont think ill go over 1.85v.

I do have good cooling (slk900 and a tornado) and i live in NYC so its not too hot out and its getting colder.
 

CalsonicGTR

Member
Joined
Nov 6, 2001
Location
Illinois
Unless you are watercooling or using some other form of extremem cooling, I wouldnt recommend pushing the CPU over 1.9V for any extended period of time. Since you have a pretty god cooling setup, you could try going for voltage over 1.9, just be careful and watch your readings for any peculiar readings
 

hitechjb1

Senior Member
Joined
Feb 2, 2003
If you look for a definite number like 1.8 or 1.9 or 2.0V, I don't have an answer for a particular CPU. This is a guideline about absolute rating on Vcore derived from an AMD datasheet for Tbred/Barton.

hitechjb1 said:
...
Max Vcore for Tbred B and Barton

There are some slight difference between the various Vcore rated CPU, due to the internal threshold voltage and leakage current characteristic of the transistors from manufacturing process variation (I think). As a result, if going into technicality and hair splitting, DLT3C (1.5V rated Vcore) is 100 mV lower than DUT3C, and DUT3C (1.6V rated Vcore) is 50 mV lower than DKT3C (1.65V rated Vcore), in Vcore absolute rating.

According to the AMD datasheet for model 8 and 10:

Data sheet for Model 10 (Barton)

Data sheet for Model 8 (Tbred)

In Chapter 8,

Quoted:
"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."

The absolute rating for Vcore = Vcc_core_dc_max + 0.5 V

Vcc_core_dc_max = Vcc_core_nominal + 0.05 V
Vcc_core_ac_max = Vcc_core_nominal + 0.15 V

Vcc_core_nominal = 1.50 V for DLT3C
Vcc_core_nominal = 1.60 V for DUT3C
Vcc_core_nominal = 1.65 V for DKT3C

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, e.g. 2600+
Vcc_core_dc_max = 1.65 + 0.05 = 1.70 V
The absolute rating for Vcore = 1.70 + 0.5 = 2.20 V

The numbers are the same for model 10 (Barton).
For Barton (DKT3C), e.g. 2500+, 2800+
Vcc_core_nominal = 1.65 V
Vcc_core_dc_max = 1.65 + 0.05 = 1.70 V
The absolute rating for Vcore = 1.70 + 0.5 = 2.20 V


The above is based on my interpretation. Pls read the datasheet, and make your judgement.


How much voltage can be applied to a CPU

There are two components of power going into a CPU at a given Vcore:

1. The "good" CV^2f active power which powers the CPU to run at frequency f.
2. The "wasted" V^2/R static power which biases the CPU as leakage current, but also heats up the chip.

Putting in higher Vcore would generally let you clock faster (CVcore^2f). But unfortunately, it also heats up the chip (Vcore^2/R).

So on air, at lower temperature 10-20-30 C, the CPU can be clocked faster and faster at a rate about 130-140 MHz/100mV (for Tbred B, Barton). So far so good. But at the same time, the chip will begin to heat up due to Vcore increases (the V^2/R compoent and also from the active CV^2f component). As a result of heat, the electrons move slower inside the chip and the CPU begin to run slower, the above rate delf/delVcore begins to drop to 120 then 110 then 100 then 50 MHz /100 mV when die temperature reaches beyond 30 C, 40 C, 50 C, ... correspondingly for Vcore above 1.7, 1.8, 1.9 V, ... The heat increases at a rate faster than the Vcore increase to slow down the chip.

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. 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.

...

For more details, you may refer to

Relationship of clock, die temperature and Vcore (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)

Some numbers to determine max CPU overclocking frequency - Vcore vs temperature,
When do the CPU's slow down?
(page 13)
Explanation (page 13)


There is another recent thread discussing related topics:

Highest everyday voltage for DLt3C?