Video card Volt mod question

peonyu

Platinum Member
Mar 12, 2003
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Hey, nubish question here but here goes. I have all the parts together to volt mod my 4850 video card, however I am stuck on one issue and I want to get everything right.

The issue is my Potentiometer [trimmer/pot], it has three prongs on it. 1 in the middle of the pot and two on the bottom of the device. Im not sure which of the prongs I should use as the ground. Should the middle prong go to ground, and one of the other prongs go to the solder point by the GPU? Or is it the other way around, or doesnt matter at all which of the prongs is used as ground ?
 

thilanliyan

Lifer
Jun 21, 2005
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You're using one of those large 3 prong pots for volt modding? It's hard to get fine control on those. Do you have a pic of the one you're using?
 

peonyu

Platinum Member
Mar 12, 2003
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This is the one I picked up today from radioshack -

Specs are -

General Features
Model 271-284
Product Type Trimmers
Body Material Metal

pRS1C-2160211w345.jpg


Its not large at all either, its actually smaller than I thought it would be. Its about the size of a penny width wise, and not much larger in height than that.

According to the guide I am following, one of the prongs needs to be hooked up to ground and 1 goes to the solder point by the Gpu. The guide isnt clear on which ones to use, except that the middle prong is used and only 1 of the other prongs is used. One of them is not used at all. I was hoping someone would have a idea as video card volt mods are all similar in concept when it comes to pots.
 
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thilanliyan

Lifer
Jun 21, 2005
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Usually, for those types of pots (if you don't need feedback from the loop), the middle is ground, and positive is connected to the left or right. If you connect + to the left, turning the pot to the left increases resistance. Use a multimeter to check this is correct. You do have a multimeter right (you better lol :))?
 
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peonyu

Platinum Member
Mar 12, 2003
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Yea I do, that sounds right for the pinout on the pot. I have everything ready to do it, but im going to wait a few days...My soldering skills really suck and Ive been testing on a dead mobo to connect wires and they are not holding well at all. So id rather be half decent at it before trying it on a good video card =p. Thanks for the help btw.
 

peonyu

Platinum Member
Mar 12, 2003
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Just a update but I did the mod last night and had no issues with soldering, turns out that my soldering skill was only a small part to blame when I considered trying before...The tip that was on my iron had oxided down to the copper, so thats why it wouldnt solder for shit originally. I replaced the tip with a craftsman hex screw tip, didnt think it would work since that tip is meant for a drill and not a iron...But it worked flawlessly.

As far as the ground goes, yea the guide said to use the middle prong as power but I used the middle prong as you said, as looking at other mods everyone also uses the middle prong...So either it doesnt matter or techpowerup made a typo [im still trying to figure this shit out completely :)].

As for the mod its on an its working fine. The voltage I dialed up from 1.15 to 1.33v/. But I have another issue now, I get a driver display error after awhile in Furmark when I crank the Mhz up. I dont know if you are familiar with HD4000 cards but my Memio peaks at 130c under the OC load, then it gives out. Im guessing the memio heat is the problem but not sure on how to bring that temp down.

Ok as far as memio goes, i didnt seat my heatsink correctly. Im using a old 2500+ copper core stock barton Heatsink on my card and one of the screws is not properly seated....So ya going to fix that. That should help the temps out to. :)
 
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tweakboy

Diamond Member
Jan 3, 2010
9,517
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www.hammiestudios.com
I thought you can software volt mod that. I guess not just the 5xxx series I guess. Very risky to solder your mobo and mess with a expensive video card. YOu have guts Ill tell you that.

At the end you might get 800 more vantage points but games will play the same there will really be no frame rate difference,,, u wont notice a change. Not worth it don't do it. gl and gl
 

peonyu

Platinum Member
Mar 12, 2003
2,038
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Supposedly you are able to soft mod these to an extent [key word is supposedly]. The stock 3d is 1.15v. I have tried alot of different bios's and never managed to get 1.2v myself, my bios may say 1.2v but the multi meter always told me 1.15v. So perhaps that is something of a videocard myth with the 4850s [lol].


As far as soldering goes its really not as hard as it looks like, it just requires some experience with a soldering iron. It took me a good week of messing with one to get it down, but once you do its easy to use. Sort of like riding a bike. But yea its not for everyone. As far as framerate goes I disagree, if its your video card bottlenecking your system, the gains are well worth it. Using a 4850 with a 4.3ghz cpu was a definate bottleneck on my end and upping the mhz by 15 to 20 percent over stock netted nearly equal fps gains in video card heavy games.
 
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thilanliyan

Lifer
Jun 21, 2005
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Whoa those temps are way too high. Yes I had a 4870 before and was watercooling it to keep temps under check when overvolting. Mine never went above 60C (GPU, memio)...even the VRMs since they had a separate cooler. You should deal with the cooling before trying to shove that many volts through that card. You might end up killing it. I believe the memio is part of the core and if that's hitting 130C, you definitely want to back off. And also, I believe there is some over current protection so you may not be able to put that much voltage through the card and actually put a load on it.
 

Tempered81

Diamond Member
Jan 29, 2007
6,374
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memio is a core temperature, sounds like it's too hot, i've never seen my 4850's memio do >103C. I also couldn't do over 1.15v actual without a pencil mod. Most core speed i could do was ~720mhz before artifacting. Did you get any gains going from 1.15 -> 1.33?
Good to hear you wired your pot correctly. Xtremesystems forums is a good place to get hard volt-mod help.

Most of the pics i've seen show a small blue pot (and the resistance range is important also). I guess those smaller ones have a more fine-tuned approach. Maybe 3 complete turns for a few hundred millivolts. Is yours sensitive to a slight change on the dial?

One thing i love about my 4890 is it has software programmable volterra voltage regulators. The masters for both memio, memory, and core vgpu are all programmable in rivatuner.
 

peonyu

Platinum Member
Mar 12, 2003
2,038
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Whoa those temps are way too high. Yes I had a 4870 before and was watercooling it to keep temps under check when overvolting. Mine never went above 60C (GPU, memio)...even the VRMs since they had a separate cooler. You should deal with the cooling before trying to shove that many volts through that card. You might end up killing it. I believe the memio is part of the core and if that's hitting 130C, you definitely want to back off. And also, I believe there is some over current protection so you may not be able to put that much voltage through the card and actually put a load on it.

Yea the temps are crazy high, im not running 3d apps until I sort this out...But the last one I ran [before it dawned on me to run gpuz to monitor temps to see if that was the problem..] showed memio @147c before crapping out :/. The gpu itself hit 94c max, which is not to bad considering the stock cooler ran it at 102c. I need to buy some screws to properly reseat the heatsink, I did a poor job of it when I added it on last week [it is not even at all, but is touching the core].
 

thilanliyan

Lifer
Jun 21, 2005
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Yes definitely deal with the cooling and go aftermarket cooling if you can. The stock heatsink is barely adequate on the 4850 from what I've read.
 

peonyu

Platinum Member
Mar 12, 2003
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memio is a core temperature, sounds like it's too hot, i've never seen my 4850's memio do >103C. I also couldn't do over 1.15v actual without a pencil mod. Most core speed i could do was ~720mhz before artifacting. Did you get any gains going from 1.15 -> 1.33?
Good to hear you wired your pot correctly. Xtremesystems forums is a good place to get hard volt-mod help.

Most of the pics i've seen show a small blue pot (and the resistance range is important also). I guess those smaller ones have a more fine-tuned approach. Maybe 3 complete turns for a few hundred millivolts. Is yours sensitive to a slight change on the dial?

One thing i love about my 4890 is it has software programmable volterra voltage regulators. The masters for both memio, memory, and core vgpu are all programmable in rivatuner.


until I reseat the heatsink properly its to early to make an exact measurement of the gains. But i can say that my old max was 700mhz stable, and 726 was semi stable [crash after a hour]. 750+ was a no-go, I would just get a black screen if I even dialed that in. When I tried 775 earlier with the vmod on [before I noticed the heat issue] it ran without a hitch until the memio crepped up. So there are definate gains from it, average oc from 1.35 is 850-900, I can think I can hit that once the heat is sorted out.

As for the pot, A small turn on it would raise the gpu by .1v,so I had to be careful since it wasnt a '20 turn or 15 turn' style pot that holds your hand, but its not bad at all. To overvolt and kill a card with the radioshack pot, you would need to knowingly turn it to much.
 
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peonyu

Platinum Member
Mar 12, 2003
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Reseated the heatsink, memio maxes out at 98c now, gpu at 92c in furmark...So have alittle bit of room to mess with. This is at 800mhz now, so heat was definately rocking my system earlier. And on that note Ati makes some damn good parts to be able to withstand 147c.
 

BD231

Lifer
Feb 26, 2001
10,568
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So it's reliable at 800 with this mod? Might just do this myself if it is, my 4850 seems to crap out anywhere past 750.
 

peonyu

Platinum Member
Mar 12, 2003
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Stable so far, going to mess with it more tomorrow. im aiming for 900
 

peonyu

Platinum Member
Mar 12, 2003
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Yea Id prefer it running alot lower than 90c myself, but short of watercooling or a aftermarket cooler its not gonna happen. These chips are mini-infernos lol. But that temp is the absolute max from Furmark, most apps other than that [including Crysis] are showing it peak at 81c. As far as the OC goes, I must have something of a dud as 800 isnt completely stable now @ 1.3 but 775 is...900 ? No way at this rate. I might tick the voltage up a tiny bit to get a stable 800 and tack on another fan, then leave it at that. Anyways thanks for the help thilanliyan.
 
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