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VCore fluctuations

S

SiliconValley

Limp Gawd
Joined
Sep 22, 2005
Messages
226
e6600
Asus P5W Dh Deluxe
Vista Premium

My VCore in BIOS is 1.4. In Vista, it's 1.38. Under load, it drops to 1.36. Is this fluctuation between 1.38 and 1.36 under load normal/acceptable? Running two instances of Prime 95 to put it "under load."
 
yes, perfectly acceptable. as the cpu comes under load it draws more current. Voltage = current x resistance. The components that make up the VRD (voltage requlator down) circuit that feeds "clean" power to the cpu have small internal resistances, as more current flows through them on the way to the cpu, the voltage drop across them increases per the above formula and these losses reduce the actual voltage delivered to the cpu. Feedback and sense circuits can adjust for some of this loss but are expensive and not perfect.

you are drooping .04V

.04/1.40 = 2.8% trivial

you can always give it another nudge of voltage in the bios to compensate for the actual under load voltage delived to the cpu. Keep an eye on temps.
 
BillParrish said:
yes, perfectly acceptable. as the cpu comes under load it draws more current. Voltage = current x resistance. The components that make up the VRD (voltage requlator down) circuit that feeds "clean" power to the cpu have small internal resistances, as more current flows through them on the way to the cpu, the voltage drop across them increases per the above formula and these losses reduce the actual voltage delivered to the cpu. Feedback and sense circuits can adjust for some of this loss but are expensive and not perfect.

you are drooping .04V

.04/1.40 = 2.8% trivial

you can always give it another nudge of voltage in the bios to compensate for the actual under load voltage delived to the cpu. Keep an eye on temps.
Click to expand...

Wow, great answer. Thanks! I'm loading with two instances of prime95 at around 61-63C depending on ambient air temps at 3.2Ghz. So far it's 100% stable and running Prime95 for about 12 hours. I think I'm going to push it a bit higher tonight and see what happens. I know it's hard to predict but does 3.6Ghz look attainable with my numbers (temps) so far? Oh, and the fan on my Tuniq 120 is at 50%, so I might have a little more room for cooling.
 
LOL dont want to discourage you, you will make 3.4 easy I bet,

I am a chicken. 1.4 vcore and and/or 65C under load and I would bail. Of course you have to do some testing just to see what she will do ;) , but back off for everyday.

Man I need a cpu with a higher multi :(
 
BillParrish said:
LOL dont want to discourage you, you will make 3.4 easy I bet,

I am a chicken. 1.4 vcore and and/or 65C under load and I would bail. Of course you have to do some testing just to see what she will do ;) , but back off for everyday.

Man I need a cpu with a higher multi :(
Click to expand...

Even though I'd love to hit 3.6 just to say I did, 3.4Ghz is really my goal. Just to clarify, do you mean if I'm running at 3.4Ghz at 1.4 and 65C load that I should bail on those setting and crank it back down or just go no further? Also, I don' t yet have a 120mm front intake fan and my Tuniq fan is only at 50%, so I think I still have some room to improve. Also, the 1.4 Vcore is just the number I started with, I might be able to crank it down and be stable. Ah, lots of testing to do. I think I'll take her up to 3.3Ghz tonight...
 
I agree with Bill's observation on your max oc.. I can run stable at 3.2ghz on default vcore, but still didn't make 3.6ghz... I got to 3.5ghz on 1.50v.. 3.6ghz was never stable no matter what kind of vcore I dumped in it.. on water at the time also.. anyways.. seems like these c2d's with 4mb cache have about 200 to 300 more stable mhz in them once you hit the point when you need to add vcore to stablize things... very similar to the dual core opterons from my experience... granted each chip is different, so ymmv. hitting 65c is like the max temp you should run at really.. for 24/7 use keeping things in the mid 50s would be better.. my cpu on air @ 3.5ghz and 1.50vcore peaks @ 60c.. that's a bit out of my comfort range so I am going back on water.. well coolit freezone.. water + tec.. anyways.. intel says 65c is the max safe limit for c2d chips.. so try and keep it there or under for safety.

best of luck to you! :)
 
wanted to get opinions on my chances from others. at 1.2volts i can get 3 gig stable e6600. Right now I have the stock heatsink/thermal paste and the temps were still getting to 63C under load at 1.2 (set to 1.275 in bios and my asus p5n-e has fairly bad vdrop, going as low as 1.2) I haven't tested above 3 yet on this voltage, but just ordered a zalman 900 and AS5, so hope I can improve my temps a lot and then be able to up the voltage. At 1.4 voltage right now my cpu got to 80C under load. If the zalman 900 lowers temps to an acceptable level do you think I may have a chance of hitting 3.5-3.6?
 
Even though I'd love to hit 3.6 just to say I did, 3.4Ghz is really my goal. Just to clarify, do you mean if I'm running at 3.4Ghz at 1.4 and 65C load that I should bail on those setting and
Click to expand...

oh no, if you can do that you are golden and I would use for day to day. just watch it for first couple of game sessions. those are my target limits for day to day, I had this sucker up to 1.5V 492FSB 70C but the board crapped out on me, all it would do for FSB, I could do 485 stable but temps were just a tad high and I didnt like the high Vcore so I back down.

I am just making recommendattions and i am very conservative so it wont hurt a bit to stretch them a bit if you find a nice round number that makes you happy :)
 
Do the vdroop pencil mod and thatll stabilize the voltage.... my commando at 1.6v in bios will idle at 1.55v and drop to 1.53 under load before the mod.... After teh mod itll idle at 1.59v and 1.6v with load:D .... All you need is a pencil to do it, seach for it at Xtremesystems.org..
 
Running at 3.3Ghz (367*9) now with load temps (2xPrime95) of 64C (Coretemp - 3-4C lower in TAT). Getting close to that magic 65C number. Stable so far but still testing. Will adding a front 120mm fan (which I plan to do) make much of a difference?
 
SiliconValley said:
Running at 3.3Ghz (367*9) now with load temps (2xPrime95) of 64C (Coretemp - 3-4C lower in TAT). Getting close to that magic 65C number. Stable so far but still testing. Will adding a front 120mm fan (which I plan to do) make much of a difference?
Click to expand...

I believe it will help a little, and hey if you want 3.4 and it runs at 67C so what, remember most games are single threaded and and even in a heavy gaming session with one core maxed at 100% and alt tabbing to look at web page or something else, you seldom if ever going to have BOTH cores at 100% .

also even with the temp stuff turned off in bios the cpu will protect itself against over temp.
 
BillParrish said:
I believe it will help a little, and hey if you want 3.4 and it runs at 67C so what, remember most games are single threaded and and even in a heavy gaming session with one core maxed at 100% and alt tabbing to look at web page or something else, you seldom if ever going to have BOTH cores at 100% .

also even with the temp stuff turned off in bios the cpu will protect itself against over temp.
Click to expand...

Yea I'm going to push 3.4 later tonight and test stability while I sleep. I've got my Super PI (1M) score down to 15s.
 
yeah - games don't work a cpu like othos with small fft's..
 
I have since added a 120mm front intake fan and it's dropped my temps quite a bit (limited testing). Okay so I went up to 3.4Ghz (378*9) and it crashed pretty fast while under load. The temps weren't bad ~60C. Here are my current OC settings:

Memory 4-4-4-12 (1:1) @ 1.95V
VCore @ 1.4
VFSB @ 1.3
VMCH @ 1.55
VICH @ Auto

I'm trying to hit 3.4Ghz and based on my temps I think I should be able to get there. I'm rock solid @ 3.3 right now. I haven't explored the possibility of going lower on VCore and checking for stability @ 3.3. I simply have always been @ 1.4 while OCing. Should I go a bit higher on VCore or am I already getting too hight? Suggestions?
 
I would do 2 things,

1) give it just a tad more vcore 1.42 something like that, I dont have your board so I dont know what the next setting is and see if that stabilizes it at your 378 x 9 setting.

2) drop you mulitplier to 8 set the fsb to 400 download memtest86+ and make a boot floppy or cd and validate your memory at 400, 2 passes , then at 425 several passes. if ok you dont have to worry any more about memory having anything to do with the stability issues. It should not as its not yet running at spec speed during the 378 x 9 adventures but I always like to rule stuff out for sure.

oh doh! have you ripped off that sheetmetal bling thingy off of your northbridge heatsink ? If not, see if it will come off. One day you will want to rework that entire heatpipe with AS ceramic and proper screws washers and nuts to hold it down, put a fan on the NB and lapp the tuniq if you did not already do it. Its a full days work but reliability will be improved as the factory workmanship always seems lacking in those details. After you get it off, do an orthos run and stick you finger on the NB heatsink and count slowly to 10 and see how far you can get before you have to take your finger off.


I did mine and it really cooled things down, obligitory pimp my rig link incoming , look at the second pic, you can just make out where the crappy push pins were replaced by screws (can just make out the nuts) and I ripped apart an el-cheapo hard drive cooler for three 40mm fans and slapped them on, your layout makes the fans for the VRD mosfets a bit more of an issue but something can be done. http://mysite.verizon.net/ressdxka/id3.html

we are keeping in reserve the ability to drop the mulitplier to 8 and run 8 x 425 to see if a northbridge strap is in the way, want to check the memory first.
 
In case you were considering some of the other suggestions in this thread this is some killer info I just found. Explains it even better than I did, bit more technical but hey, we both migh learn somthing, one thing I did not like is that while it is true a 4 phase excellent VRD design is better than a crappy 8 phase design he failed to emphasise a good 8 phase is better than a good 4 phase. /shrug.

http://www.thetechrepository.com/showthread.php?t=126

ouch, man that stings, well maybe best just to pull out the interesting part. Vdroop is needed for stability which in this case means ensuring that under rapid changes in current demand, like starting or stopping Orthos, very undesirable spikes in voltage do not occur. (and there are still increased losses thru the components as current increases it just taken into account in the design)

VCC (Vcore) and Vdroop Explained

Load line droop (or Vdroop) is an inherent part of any Intel power delivery design. A current proportional to the average current of all active channels flows from through load line regulation resistor RFB. The resulting voltage drop across RFB is proportional to the output current, effectively creating an output voltage droop with a steady-state value. Equation 2 dictates the value for RFB that should be choosen to satisfy the Intel VRD specification (the source of RLL) based on a) the number of power delivery phases (N) and b) the equivalent series resistance (ESR) of the inductor used, effectively known as DCR.

The first question that may come to mind is why droop voltage at all. Truthfully, in most cases the designer may determine that a more cost-effective solution can be achieved by adding droop. Droop can help to reduce the output-voltage spike that results from fast load/current demand changes. The magnitude of the spike is proportional to the magnitude of the load swing and the ESR/ESL of the output capacitor(s) selected. By positioning the no-load voltage (VNL) level near the upper specification limit (bound by the Vccmin load line), a larger negative spike can be sustained without crossing the lower limit. By adding a well controlled output impedance (RLL), the output voltage under load can be effectively 'level shifted' down so that a larger positive spike can be sustained without crossing the upper specification limit (such as when the system suddenly leaves a heavy load condition). This makes sense as the heavier the CPU loading the smaller the potential negative spike and vice versa for lower CPU loading/positive spikes. The resulting system is one in which the system operation point is bound by Vccmin and Vccmax at all times (although short excursions above Vccmax are allowed by design).
Click to expand...

I read that as messing with the design without knowing exactly what you are doing could expose your processor to voltage spikes outside of its design limits. (and if you where already running a very high Vcore ???? !!!! )

Of course the beauty of it all is that its your stuff and you do with it as you damn well please
 
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