xsuperbgx's Volt modding, zombies and electronics learning thread.

I am going to try to learn how to do some volt modding. I know that some people are good in this area and I am hoping that those with the knowledge can help me learn. I do have some education in electronics, but it has been years.
I have a ati 4650 ddr2 (same as bobnova's) that I will start with that since it is fresh on his memory and it is right here in front of me. I also have my dead 5870 lightning that I am hoping i can use as a zombie, as well as my miscellaneous assortment of gpu's collected over the years. i have a pretty good source locally for parts as well as a collection of dead hardware that can be robbed for parts, if needed.




HD4650 ddr2

I think the vrm for the core is rt9018b. Looking at the data sheet here,

Also up6101bu8 maybe for the memory? i don't see a data sheet, but there are a few mods of this found on google:4350 mod i suppose I could copy that, but I think I would like to learn to figure this out.




sorry for cell pics.

I will bring home my multimeter tomorrow and get a baseline on current voltages and list the current abilities of the card.





I never really noticed this area: http://www.overclockers.com/forums/forumdisplay.php?f=128
It looks like there is some gems there. I will get started there.

Don't be intimidated by the following wall of text!
Every step is simple, so take it one step at a time.


Ok so the first thing to do is to find the two voltage regulators.
I happen to know that on that card they're both 8 pin jobbies. Look for an eight pin chip surrounded by an unreasonable number of tiny little components, that'll be one of them.
Generally the vGPU has more stuff around it than the vMem.

Once you think you've found them, write down the markings and search for the longest on google looking for a datasheet.
If you find one that says it's a buck controller you're on the right track

Crack open the datasheet and find the pinout, you're looking to find the FB or Feedback pin.
Once you find that, check it's resistance to GND with a multimeter. Check on a few different settings to be sure you know what the resistance is.

Now you need to find a trimmer (variable resistor) with a resistance at least ten times what you measured between FB and GND, somewhere in the 12-20x range is ideal. It needs to be ten turns minimum, more is fine. Less than ten turns end to end means that the voltage adjustment will be very coarse, which isn't safe.

Once you have the trimmer glue it to the board somewhere.
Peel some strands out of an 80pin IDE cable, these are the best wire by far.
You want to connect the FB pin to one of the trimmer pins, which one depends on which way you want to turn the trimmer to adjust the voltage (more on that in a bit).
The other pin on the trimmer should go to a switch or a jumper type connection, I use double-length pins for perfboard type stuff. Standard jumper caps work great on them.
The other pin on the jumper or switch should be soldered to GND. Now you can enable and disable the vmod easily.

On trimmer pin selection:
If you connect to the middle and rear pins, turning the trimmer counter-clockwise will raise the voltage.
If you connect to the middle and front pins, turning the trimmer clockwise will raise the voltage.

Personally I like to use the middle and rear, so that the trimmer is like a faucet. Counter-clockwise "opens" it to allow more voltage to go through.
It's a personal preference thing, but you may want to write it on the card so you do not forget!

Crucial last step! Put a multimeter on the trimmer connecting to the middle pin and the pin you did not use, now turn the trimmer till you get zero ohms (ish) between those two pins. If the unused pin to middle pin resistance is nil the resistance between the middle pin and the used pin is at maximum, and the voltage is set as low as it can go.

That does it for the vmod itself, but you'll need some monitoring for the voltages!

The easy way to do this is to find the largest capacitors between the GPU regulator/MOSFETs and the core, and between the Memory MOSFETs and the memory, you're looking for something rated in the 2.5v to 6.3v range. If it's rated at 16v it's not the right cap.
Anyway, the positive leg of those capacitors (a note: the negative leg is the one marked on the capacitor! No clue why) will be the vGPU or vMem output, you can solder your monitoring wire there.
PSU-side Molex connectors make wonderful monitoring bits, multimeter probes fit them perfectly.
I like to use the yellow wire for vGPU and the red to vMem, just to keep things straight in my head.

That guide is fantastic, Ed.

Do you think by any chance you can put together a video so we can see it in action? I've been planning to vMod my 4870 but I just haven't had/taken the time to do so. (my entire soldering experience has been modding 360s)

No particular reason to vmod a 4870 really. AB-X 1.5 does core volts plenty high, and the memory almost never scales with voltage.

That said, I'll cogitate on a video

I found these images and I am going to post them here for when I am ready to work on the lightning zombie. Someone could explain these if they would like.








From this thread.

Heatsinks hotglued to the output capacitors? What the hell?

I'll see if I can make sense of it later tonight

HD4650
Results at stock volts: Passed 3D01 at 790 core and 576 mem. 55766 http://hwbot.org/submission/2249776_
Volts right now are at 1.225 and 1.98.

After looking again, it looks like both vrms are the up6101bu8.


(found at ocn)


The fb pin at the vrm (core) is 6.84 k
The fb pin at the vrm (mem) is 4.17 k

So I can use a couple 100k. Or a 50k and a 100k.

Look at what I have. I scrounged some on the right and bought a variety of 10 turn pots as well (left.)

You should be able to stomp all my scores into the ground, even with Untouchables.
My memory is complete junk

It didn't seem the volts helped your memory much. So I am not thinking it will boost me much... did you mod only the core and mem? I think I saw somewhere that there was a vddci mod also.


I also bought a new tip for my soldering iron and a magnifying glass with an adjustable stand.

I was contemplating looking for the vddci, voltage didn't help my memory much at all.

EDIT:
I believe I found the vddci regulator, not 100% positive yet.

ok I think I got it. vcore now at 1.300 and mem at 2.058.

Pics of embarassing solder job and copious amounts of hot glue coming up!

Awesome! Congratulations


I've had no luck finding VDDCI, it may be combined on the VDDC (vMem) rail.

Not my neatest work.
I will test results sometime this weekend.
Thanks Bobnova for your help.
Next up I will do a vid adjustment on my x850xtpe or maybe start on the lightning zombie....

Looks good to me!
If it works and doesn't short anything out, it's neat enough

Can I adjust voltage while powered on or do i have to shut down?

How far should I push it, until no improvement or temps get too high?

Yes, and yes.

It's the same manufacturing process as 4870/4890, and some 4890s run at 1.35vcore stock, 1.4 to 1.5 should be fine if the temps are good.
The ram, assuming it's the same chips as mine, is rated for 1.7 to 1.9v normal, 2.3v max recommended.

EDIT:
Actually, I don't recommend adjusting the voltage with the thing turned off, who knows what you'll get when you turn it on!

I decided I couldn't wait to test....
running 3d01 lobby high
Some quick results:
vgpu @ 1.345
vmem @ 2.200
Maxed out the slider in rivatuner at 900
Mem was able to increase to 590, but I ran out of time. I think it will go a little further.
Lobby high score was at about 380 max before vmods
Lobby high score after vmods at 397
I will do further testing in the next few days.

How do I get more available core speed in rivatuner?


edit :

bobnova said:

Actually, I don't recommend adjusting the voltage with the thing turned off, who knows what you'll get when you turn it on!

Click to expand...

LOL Yeah, I guess you can't. The voltages just moved so slow when I first tried to adjust so I got a little hesitant.

My rivatuner goes to well over 1000.
I did first load rivatuner when I had to card clocked to 780MHz though, so it thinks that is stock.
Try deleting riva, OCing with MSI-AB to 780ish, then reinstalling and running riva.

Alternatively if afterburner works for you, use 1.5 or 1.51 (extremes) with enableunofficialoverclocking set to 1.
When you max the slider out, close AB and reopen for a new improved slider.

damn your really gonna have to make me work for it when i do this ram swap :\