Vcore and vdimm with A64

[racinjimy]

I have one question: What is considered to be high vdimm voltage?

(i.e., is 3.2v vdimm considered high or is as high considered anything more than 2.9v)

I am running 1.325X110% so about 1.45 vcore, so I should be fine with my 3.2V vdimm

but I am interested if the threshold for HIGH vdimm is >than a certain number like 3.0V or does no one actually know for sure

I do always keep in ming that O/C is not a risk free proposition , nor is 24/7 crunching a distributed computing app at 3.2V vdimm.

[k0nsl]

Can one thing be clarified here:

If I'm running an x2 4800 stock with Vcore 1.35V and have cool n' quite enabled which drops the Vcore to 1.1V, have my OCZ EL Platinum running with 2.65V is this a problem. Meaning when the cpu is running with 1.1V due to cool n' quite and the mem with 2.65V....is that a problem.

WHat the hell IS safe.

That is not unsafe. I would think that going over 3V is where it begins to be unsafe. Correct me if I am wrong.

-k0nsl

[mouzel]

If you use C&Q you can run 1.0 V Vcore and 3.0 Vdimm for instance. That's a difference of 2.0 Volt and works fine. Maybe the voltage differential between Vcore and Vdimm may not exceed 2.5 V or something like that ?

[racinjimy]

If you use C&Q you can run 1.0 V Vcore and 3.0 Vdimm for instance. That's a difference of 2.0 Volt and works fine. Maybe the voltage differential between Vcore and Vdimm may not exceed 2.5 V or something like that ?

right so don't use C&Q if overclocking..........that is in every AMD overclocking sticky on every forum

[xgman]

So has anyone dtermined if this thread is a result of this issue?

http://www.xtremesystems.org/forums/...7&page=1&pp=25

[TheMeatFrog]

I run my bh-5 at 3.4v or 3.5v most the time so my vcore should be atleast 1.45 correct? Now is this 1.45v windows vcore or bios?

[RyderOCZ]

I would say bios or "calculated"... i.e. 1.325 + 110% = 1.4575...but that will show probably 1.41-1.43 in bios? Even if you went 1.350 + 110...that should put you at 1.45 in bios I think.

[TheMeatFrog]

Wow thanks for the fast reply Ryder!

[T_M]

Interesting that AMD suggested raising vcore

[Jochenp]

Lol, nice one T_M they suggest you void your warranty! I'm not gonna do that

[Tony]

Interesting that AMD suggested raising vcore

They didn't, they would never say that officially.

The only way to strengthen the core is with a vcore increase, thats all they will actually say.

[da-key]

Tony is not talking about cooking the chip by applying to much Vcore...he is talking about the memory controller and too much Vdimm with too Low Vcore to compensate for the increase in Vdimm.

I mean these chips can take some abuse within the limits of your cooling.

Yes I was well aware of this.
My point was that relatively few of these E revisions or any amd 64's are getting fried by us overvolting them so... BETTER SAFE THAN SORRY.
Since the risk of cooking your cpu with a few extra volts is minumum at best, so I would go ahead and follow Tony's advice.
That clarifies my observation so that it is better understood.

[[ r2 ]]

So what is a safe vdimm to run? Up to 2.9 or so?

[Rickster_64]

Like what has been posted, staying to 3V or less will basically be fine. Its those with OCZ DDR Boosters and people running @ 3.4-3.5VDIMM will need tup up their cpu voltage or risk frying their chips. I run 2.9V on my geil and 1.5V on my 3500 so I don't see myself having any issues. Tuesday I get my Opty 146, so I will have a little something new to play with.

[Kameleon]

So can we get an answer on this: What's a safe vCore to run if you're running 3.5-4V vDIMM?

[RyderOCZ]

So can we get an answer on this: What's a safe vCore to run if you're running 3.5-4V vDIMM?

There is no Spec for this...nobody gave Tony or anyone else any definitive numbers. The only thing AMD officially says is:

The only way to strengthen the core is with a vcore increase, thats all they will actually say

So just don't run Stock Vcore with High Vdimm....MY OPINION and best guess would be at least 0.05 over stock...maybe 0.1V
So if stock Vcore is 1.40...run 1.45-1.50V.

[Monge]

RyderOCZ: Very clear, thanks
Would you consider all past 3v or 3.2v as high Vdimm?

[RyderOCZ]

RyderOCZ: Very clear, thanks
Would you consider all past 3v or 3.2v as high Vdimm?

IMO yes 3.0V+ is high Vdimm.....whether 3.0V and using stock Vcore is enough to harm your CPU....who knows.......but yes I consider 3.0V+ high Vdimm

[Takumi]

Tony: do you know what the reverse breakdown voltage range is for these diodes. Knowing this could help narrow down the range of safe voltage differences.

[Micutzu]

First of all, the CPU doesn't have to do directly with the VDD, but with Vtt/Vref, wich should vary from 1.25 to 2V when you adjust the RAM from 2.5 to 4V. Maximum JEDEC Vdd voltage is 2.85V, and lowest voltage for A64 CPU's (CnQ activated) is 1.1V, so we know for sure that a difference of 0.325V between Vcore and Vtt is safe. This means that for a 1.35V Vcore voltage, we can have a safe Vdd of at least 3.35V, and for 1.5V Vcore -> 3.65V Vdd.
Probably the real danger is when those diodes go near the opening (conduction) voltage, wich should be ~0.6V for Si-based junction; if this is true, 1.35V Vcore and above 3.9V Vdd should kill the CPU instantly ... anyone wanna try ?

[Zeus]

Interesting stuff.

A while back i bought a second hand venice 3000+ 0512 that could do 2,7GHz at stock voltage.
When the former owner first got it it was able to do 290+ Mhz with TCCD, later on he switched over to redline and high voltage.

After a few months of "abuse" with high voltage i bought the CPU and tried to get it stable at 9x300 with my TCCD.

There was no way to get it stable over 260 any more.
2.7GHz with stock voltage was still possible though.

I think the memcontroller got worn out due to high voltage.

Fortunately, the seller was kind enough to let me return the CPU.

[uOpt]

Wait, so you say the RAM voltage makes a difference for the CPU?

[RyderOCZ]

Wait, so you say the RAM voltage makes a difference for the CPU?

Yes.....low (stock) CPU Core voltage...coupled with high Ram Voltage....can damage your CPU....by raising the Vcore slightly you can strengthen the CPU and prevent this damage.

[Dumo]

Heres from Dynasty post @ OPB's DFI expert thread....http://www.xtremesystems.org/forums/...8&page=3&pp=25


@ Tony, Thanks for this important info ..Hope it will save a lotta cpus

[Tony]

First of all, the CPU doesn't have to do directly with the VDD, but with Vtt/Vref, wich should vary from 1.25 to 2V when you adjust the RAM from 2.5 to 4V. Maximum JEDEC Vdd voltage is 2.85V, and lowest voltage for A64 CPU's (CnQ activated) is 1.1V, so we know for sure that a difference of 0.325V between Vcore and Vtt is safe. This means that for a 1.35V Vcore voltage, we can have a safe Vdd of at least 3.35V, and for 1.5V Vcore -> 3.65V Vdd.
Probably the real danger is when those diodes go near the opening (conduction) voltage, wich should be ~0.6V for Si-based junction; if this is true, 1.35V Vcore and above 3.9V Vdd should kill the CPU instantly ... anyone wanna try ?

you are touching on what I have tried to tell every one. its not the value of VDD, its the voltage difference between VDD and vcore on the cpu you all need to watch and keep as small as possible.