X800 xt OVP resistor question?

nycundaground · Sep 10, 2004

I have a x800 xt and id like to do the OVP mod. i know u need a 500 ohm resistor but i have in some 470-ohm and 560-ohm resistors that i bought a while back ago. Which one would u recommend me using the 470-ohm or the 560-ohm one?

L337 M33P · Sep 11, 2004

You need a 500 THOUSAND ohm variable resistor for the mod, assuming that you have the same chips.

http://www.vr-zone.com/?i=852&s=1

OCFCaTalyst · Sep 11, 2004

A fixed resistor wont work.......because no1 knows what the best resistance is. You need to play around with the resistance a bit to get it to stop crashing after a certain voltage.

-CaT

ViperJohn · Sep 14, 2004

nycundaground said:
I have a x800 xt and id like to do the OVP mod. i know u need a 500 ohm resistor but i have in some 470-ohm and 560-ohm resistors that i bought a while back ago. Which one would u recommend me using the 470-ohm or the 560-ohm one?

For starters it is not an OVP mod. The mod at R1596 is for Vcore PS Over Current protection. It
raises the setpoint where the vcore regulator will shutdown the on-card vcore power supply due
to excess current. It's function is not to protect the core but to protect the card and traces if a
Vcore PS mosfet should fail to gate off or flat out short.

The standard resistor at R1596 on an x800 is a 60C or 41.2K ohms. If you parallel R1596 with
a 42K, 1/8w or 1/4w fixed resistor the resistance will be lowered to 21.8K and increase the over
currert trip setpoint by a factor of 2 approximately. That is actually much higher than needed
to cover the increased core current draw that comes with increased Vcore.

Paralleling an 82k across R1596 will give you a final resistance around the 27K mark and increase
the set approx 50%.

Viper

El<(')>Maxi · Sep 14, 2004

The one you used on Krag's card was 100k right Viper? As far as 500k potentiometer, pc ice over @Xtreme ran a vr to 28k circut resistance and ended up with a dead card.

OCFCaTalyst · Sep 14, 2004

The ovp mod can be tricky. Really all it does it let you give higher voltages to the card without it crashing, it has NOTHING to do with stabilization. I wouldnt reccomend it, but if you do the mod, use a 500K VR.

-CaT

ViperJohn · Sep 15, 2004

El<(')>Maxi said:
The one you used on Krag's card was 100k right Viper? As far as 500k potentiometer, pc ice over @xtreme ran a vr to 28k circut resistance and ended up with a dead card.

Yes Krag's card had a 100k. I have gone to 82K since then.

One card failing after a mod does not a trend make. Running the VC current limit trip setpoint
higher by lowering the equilevent resistance of R1596 didn't kill the card but another mod might
have if the cooling wasn't good. The card may have simply died from infancy failure and would
have kicked the bucket mods or no mods. There is no way to really know.

Viper

ViperJohn · Sep 15, 2004

OCFCaTalyst said:
The ovp mod can be tricky. Really all it does it let you give higher voltages to the card without it crashing, it has NOTHING to do with stabilization. I wouldnt reccomend it, but if you do the mod, use a 500K VR.

-CaT

Again it is not OVP. R1596 controls the setpoint where the 5240 Vcore regulator starts an 8+8
clock count to to trip the Vcore PS off in the case of high current flow nothing more. It
is all in the datasheet for the chip.

You are correct that it does nothing as far as card stability. While a trim pot is totally unnecessary
if you use one a 100k would be a much better choice. It would give you far better resolution as
you would be working mid range with a lower rate of change per turn of the adjustment screw
instead about 2 1/2 turns from zero ohms with with a 500k, 25 turn trimmer.

Viper

El<(')>Maxi · Sep 15, 2004

Viper I don't think it was a cooling issues as he did the triple cascade that Oppainter used to grab #1. What would you suggest as the max core v on the X800XT with 172w pelt? Or would you determine that based on stressed temps?

ViperJohn · Sep 15, 2004

El<(')>Maxi said:
Viper I don't think it was a cooling issues as he did the triple cascade that Oppainter used to grab #1. What would you suggest as the max core v on the X800XT with 172w pelt? Or would you determine that based on stressed temps?

Well he definately had good core cooling. Maybe to good lol. When the temperatures get real
low you can run into component failure from cracking due to being brittle as such low temps. I have
grenaded my fair share of cores and components with LN2 cooling that is for darn sure. The reason
for failure list is a long one. He may have lost a Vcore PS mosfet or like I said the card may have
simply been an infancy failure death and would have died early no matter what, if anything, was
done to the card. While ATI tries to weed out the weak cards that might suffer an infancy failure
with a factory burn in some still slip through. Nothing bothers me more than modding a brand new
card. I prefer a card that has at least 200-300 hour on it as they are typically past the infancy
failure time period at that point.

Viper

OCFCaTalyst · Sep 16, 2004

Viper, OVP and overcurrent is the same thing. They increase the amount of the voltage the circuit will allow the GPU. OVP = Over Voltage Protection = same thing as overcurrent.

-CaT

ViperJohn · Sep 16, 2004

OCFCaTalyst said:
Viper, OVP and overcurrent is the same thing. They increase the amount of the voltage the circuit will allow the GPU. OVP = Over Voltage Protection = same thing as overcurrent.

-CaT

Oh so wrong. You really do need to reread the data sheet on the 5240 regulator LOL. OVP
is fixed at 2.235 volts. OCP is way different my friend.

You can get the datasheet here;
www.fairchildsemi.com/ds/FA/FAN5240.pdf

Viper

Jojo1971 · Sep 17, 2004

OCFCaTalyst said:
Viper, OVP and overcurrent is the same thing. They increase the amount of the voltage the circuit will allow the GPU. OVP = Over Voltage Protection = same thing as overcurrent.

-CaT

let's go back to the basics:

voltage is different from current..

OCFCaTalyst · Sep 17, 2004

Yes voltage is different from current grrrrr...........im just trying to make it easier, it does the same thing bro, it lets u raise vgpu past a certain point taht you couldnt before the mod, so in most peoples eyes, its OVP. This OCP and OVP horse **** is jus gonna confuse ppl lol. We can get technical all we want, but it will be me n u in this thread bc evry1 else will be thinking WTF.

-CaT

ViperJohn · Sep 17, 2004

OCFCaTalyst said:
Yes voltage is different from current grrrrr...........im just trying to make it easier, it does the same thing bro, it lets u raise vgpu past a certain point taht you couldnt before the mod, so in most peoples eyes, its OVP. This OCP and OVP horse **** is jus gonna confuse ppl lol. We can get technical all we want, but it will be me n u in this thread bc evry1 else will be thinking WTF.

-CaT

You are not making it easier when you are wrong as they are not even close to doing the same thing.
OVP and OCP are two separate and very different functions of the regulator. It is technical issue as
OVP has absolutely nothing to do with you not being able to run higher Vcore and OCP very seldom
does either.

Viper

El<(')>Maxi · Sep 18, 2004

Hey Vip could you answer my voltage question

I'm going to mod a Gigabyte PE if I ever get the damn thing

OCFCaTalyst · Sep 18, 2004

ViperJohn said:
You are not making it easier when you are wrong as they are not even close to doing the same thing.
OVP and OCP are two separate and very different functions of the regulator. It is technical issue as
OVP has absolutely nothing to do with you not being able to run higher Vcore and OCP very seldom
does either.

Viper

Well in this case it does, because many people who are complete the mod say that they can give higher vgpu. I already said OCP is different from OVP, i dont dispute that, u can handle this thread now.

-CaT

X800 xt OVP resistor question?

nycundaground

Member

L337 M33P

Member

OCFCaTalyst

Member

ViperJohn

Senior Radeon Mod God

El<(')>Maxi

Blank Senior Member

OCFCaTalyst

Member

ViperJohn

Senior Radeon Mod God

ViperJohn

Senior Radeon Mod God

El<(')>Maxi

Blank Senior Member

ViperJohn

Senior Radeon Mod God

OCFCaTalyst

Member

ViperJohn

Senior Radeon Mod God

Jojo1971

Member

OCFCaTalyst

Member

ViperJohn

Senior Radeon Mod God

El<(')>Maxi

Blank Senior Member

OCFCaTalyst

Member

Similar threads