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GKirev

HD4870 | Oldschool boys | OVP | VT1165MF

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Hello! 

I have a few old GPUs lying around and i decided to get the soldering iron and blow up some of them :D

I always wanted to learn to overclock GPUs. I started with the Shunt mods, then learned to solder and look at datasheets, but now I found out my worst enemy - over voltage protection :D

I built myself a chiller, however i am unable to use it since this OVP hits me. It hit me on my 770 (managed to hit 1.299 volts MAX) and now I am fighting with this 4870. Can't go over 1.499v. 

I would really appreciate some experienced old school guys to explain how the OVP works on this thing. (or in general) I was reading the datasheet of the VT1165MF and the NCPsomething of the 770, but i was not able to understand how the over voltage controller circuit manages the maximum threshold. 

All of the information i find on the internet is old threads with missing photos and i cannot even trace the pins with my multimeter... 

I have basic electronics knowledge, so do not be afraid to be prompt. 

Any help would be appreciated, and since i used to run a small GPU refurbishing business - i have a lot of old GPUs laying around - might as well send one out or sell at a really low price as a gift to someone.

I plan on pushing this card to the limit and might as well share my experience here :)

Thank you, guys.

hd4870_03.jpg

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That Volterra controller is fully programmable.

What do you set voltage with? I've used the VT1165 plugin for RivaTuner in the past. There was a similar thread recently and they suggested VoltageFactory tool: https://community.hwbot.org/topic/193668-gtx-260-ocp-ovp-need/

According to the documentation, when in SVID mode, you should be able to set voltage even above 2V.

As for OVP in general, the OVP trip point is usually set as an offset value (in mV) relative to the programmed VID or the nominal voltage. To lift that limit you have to re-programm the VID. On the NCP controllers, usually that's the only way.

VID is set with bunch of resistors (or empty pads) each representing a single bit (0 or 1). You can configure them according to the VID table in the documentation of the controller you're working with. Normally, you don't need to touch all of the resistors.

Programming a higher VID (nominal/starting voltage) lifts the trip point, although the tolerance you have is still the same if you don't have a way to increase it or disable it completely. After changing VID, you can still use that FB/Sense pin mod to increase output voltage. For example, a common NCP3588 on older cards has a non-adjustable OVP threshold.

 

Edit: I remembered that TechPowerUp's GPU Tool also works with HD4890: https://www.techpowerup.com/download/gputool-community-technology-preview/

Edited by I.nfraR.ed
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