Epox 8KHA+ Vcore mod question!!

[Paul.K]

Thanks in advance guys!!!

Now after running my XP1900+ for a few hours at default speed I decided to increase the FSB to 150 which gave me a reading of 1800Mhz. Now my Vcore mod on my Epox 8KHA+ was completed several weeks ago. My problem is, whenever I increase my Vcore to 2.05+ my system will load into XP no problem and I can play games for 30-minutes to 1 hour after that the machine reboots. Now if I increase the Vcore to 2.1volts it will load into XP but opening a intensive application will cause the machine to reboot. I then tried it with a lower Vcore setting at it ran again for 30 to 1 hour duration before rebooting. Whats the reason for this???
Also for your information I have a Sparkle 400Watt PSU modified to provide a high 5volt and 3.3 volt lines.

Please help because I know this chip can do 1.85Ghz+!!!!

Please note the machine operates fawlessly with a Vcore of 2.01 volts and I have experienced no reboots.

I have a 220 linear pot connected to pin2 and this is earthed too my drive bay lever................


Thanks for all your help!!!

Anyone experiencing the same problem I'm having???

[dimmreaper]

I had the same issues Paul. A fan blowing on the voltage regulator corrected it.

[Paul.K]

dimmreaper,

I have a small heatsink on mine. However how much of an increase in Vcore could you achieve with a fan blowing on the VRegulator chip, before the rebooting aquired. I have to say my IWill KK266R could reach 2.34volts and had no rebooting issues. Could it be also that the motherboard has a onboard protection circuit thats does not allow the Vcore above a certain voltage level?????? Or could it be because of a varying Vcore a high voltage spike could trigger the voltage protection mechanism on the board....


I wish I could reach 2.2Volts!!!!!!!

[dimmreaper]

Without the fan, I couldn't run for very long at any voltage with my 200K resistor in place. Anything above 2.05V would wuss out with a 220K resistor in place.

We just have got to remember that this part was never really intended to function this way. When you push the envalope, sometimes problems arise, and you have to deal with them.

[Paul.K]

Hey Dimmreaper,


I'm just after doing a few experiments, now I attached a fan to the voltage regulator chip which was pushing 30cfm of air on to the chip. These are my results,

2.14 Volts boots to Win XP but soon after reboots
2.1 boots to WinXP but after 20mins-45mins reboots
2.08 same as 2.1volts
2.04 no problems.


From the above results I dont think temperature is an issue here since placing a fan on the voltage regulator chip made no difference my Vcore. I can only conclude that the chip or some other factor does not like a Vcore above 2.04 volts......

Maybe Epox Tech can help!!!!

[dimmreaper]

Originally posted by Paul.K
Maybe Epox Tech can help!!!!

I sure hope so . . .

[proze]

might be the psu fading cos of the tweaking. didn't you have issues like that, jeff?

[dimmreaper]

Originally posted by proze
might be the psu fading cos of the tweaking. didn't you have issues like that, jeff?

Nope . . .

[dimmreaper]

Paul.K, wonder if it is some type of problem with your Vfb circuit spiking or surging for some reason. This would, in theory, cause the voltage regulator to "throttle back", and actual Vcore to drop off. I dunno, just trying to throw some Idea's out for yah . . . .

[EPoX Tech]

In my findings Athlon XP is both very variable in overclocking performance and also is not too keen on voltage unless cooled sub zero or at max to about 4° or 5°C above.

It does tend to freak at the high voltages unless active cooled - perhaps due to the fact that the "smaller" part of the core does not like the voltage. A small portion of the Palomino core is manufactured on a hybrid process that appears to be smaller than dot one eight according to some professional articles.

[Below Ambient]

TOO HOT!!! i found that after mounting a remote sensor onto the side of my core that the onboard sensor is in between 13-22C off the actual chip temperature... your chip is WAY too hot... i consider 1.95 the absolute max for air-cooling..... any more and i get reboot problems no matter what board im using....

[Below Ambient]

oh yeah BTW not to be too negative but you're having the EXACT same problem i had with my 8KHA+ and i finally just took it out and put my 8K7A back in....im thinking that certain batches of 8KHA+'s had voltage problems and doing a volt mod just makes things worse....in my experience

[dimmreaper]

Originally posted by Below Ambient
the onboard sensor is in between 13-22C off the actual chip temperature

I've done extensive amounts of thermal solution testing with my board. I can't really go in depth about why I've done so much testing, as this would violate the forums policy on advertisement. IMO your WAY off base here. I've found my board to report temperatures 2-3 degrees higher than those determined by the method recommended in the AMD Thermal, Mechanical, and Chassis Cooling Design Guide.

I have found that different thermistors will report the same temperature differently. This could lead to a difference of several degrees when comparing motherboards of the same make and model. But still, your experience is radically different from mine, too different for me to accept as fact.

[EPoX Tech]

This is something I have done a lot of work with and the figure of 13-22°C can only be a complete fabrication.

Jeff states correctly the implementation within the specification tolerance of the AMD whitepaper.

[proze]

erm.. i have cpu temp measurement that i'm pretty sure is almost 100% accurate, and i get the difference between my mobo and real temp to be 3C MAX. the motherboard thermistor on my 8kha is prolly 2C too low on average. it's less of a difference at higher temps than lower ones, which i suppose is also good. more accuracy at higher temps is what you want.

[Road_Runner]

same problem here alluded to in thread I posted a few minutes ago here...Can you Epox guys help here?
My 8KHA+/1800xp runs great at 1770 at 2.03v with a 250k ohm resistor for the vcore mod. if I give it the slgihtest bit more voltage(1 fsb higher), all hell breaks loose with random reboots, or won't boot at all (dies trying to get in Win2k). Prime95 will kill it immediately and reboot the system at anything higher fsb/voltage-wise. And this can be with the temp showing 35c. I can run 1770 Prime95 all day long and hit 38c for hours with no problems.

Don't think it's heat related as I run 35c idle and 38c load using onboard thermistor on pretty well cooled watercooled system.

Currently at 24c sys temp and 34c proc temp. I just know this chip has alot more than 1770 in it.

And yes, I am plagued with the reboot/use rest button issue as well.

[EPoX Tech]

Originally posted by Road_Runner
same problem here alluded to in thread I posted a few minutes ago here...Can you Epox guys help here?
My 8KHA+/1800xp runs great at 1770 at 2.03v with a 250k ohm resistor for the vcore mod. if I give it the slgihtest bit more voltage(1 fsb higher), all hell breaks loose with random reboots, or won't boot at all (dies trying to get in Win2k). Prime95 will kill it immediately and reboot the system at anything higher fsb/voltage-wise. And this can be with the temp showing 35c. I can run 1770 Prime95 all day long and hit 38c for hours with no problems.

Don't think it's heat related as I run 35c idle and 38c load using onboard thermistor on pretty well cooled watercooled system.

Currently at 24c sys temp and 34c proc temp. I just know this chip has alot more than 1770 in it.

And yes, I am plagued with the reboot/use rest button issue as well.

I've just made you a response in the other thread

[Road_Runner]

Originally posted by EPoX Tech


I've just made you a response in the other thread

thanks...got it.

[EPoX Tech]

BTW - love the RoadRunner graphics indeed.

[Road_Runner]

Originally posted by EPoX Tech
BTW - love the RoadRunner graphics indeed.

Thanks.................beep beep.........