ATI 4850/4870 voltmod thread

[W1zzard]

oh .. so he maybe ended up with 0 ohms and fried the card ... the temperature drift of the VR is probably bigger than 50 ohms

[Theta]

Yep, it fried when the VR drifted to 0... I'll bet money on it.

We're talking about 50 OHMS here, people... not 50K.

[STEvil]

How much voltage is at the mod point?

Could be that at the extremely low resistance levels the voltage is causing excessive amperage to overheat the VR.

[jimmyz]

Yep, it fried when the VR drifted to 0... I'll bet money on it.

We're talking about 50 OHMS here, people... not 50K.

still working good on yours right? get any records yet?

[Theta]

Still good here, nothing major. I don't have water, so I'm not pushing past 1.35v. Up to you guys to go up to those heights.

The VR was never warm under testing, but now I'm using 1W fixed resistors - more insurance of no drift, as I'm sure you guys will agree. Too dangerous with a VR at these low ohms.

[CCC]

MMOuse said he'll show ya 4870 cf on ln2 and vmods later on tonight

[Theta]

MMOuse said he'll show ya 4870 cf on ln2 and vmods later on tonight

Sounds like a plan!

[Clemmaster]

Why would it overheat the VR? Let say we have 3v in VR plots --> P = U²/R = 9/50 = 0.18w ...

Assuming that the tension deliverd to the chips can't be >3v and that the VR value can't be <50, you'll always be <0.18w.

On 8800GT, the Vgpu mod is done with a 500 ohm VR...

[SNiiPE_DoGG]

so this resistor seems to be ideal for the mod? 50 ohm 15 turn .75W (is .75w ok? could you go to .5w for a 25 turn Pot?)

[jimmyz]

so this resistor seems to be ideal for the mod? 50 ohm 15 turn .75W (is .75w ok? could you go to .5w for a 25 turn Pot?)

yep looks great.

[Clemmaster]

Still good here, nothing major. I don't have water, so I'm not pushing past 1.35v. Up to you guys to go up to those heights.

The VR was never warm under testing, but now I'm using 1W fixed resistors - more insurance of no drift, as I'm sure you guys will agree. Too dangerous with a VR at these low ohms.

Put a fixed resistance and a VR in serie if you fear this

[Vlad_13]

My god, this card requires MASSIVE cooling for the voltage regulators. I had previously cut the original heatsink and used that, but over 1.4v it just gets into the 80c and over range. I just modded a cpu heatsynk to fit the voltage regulators and it seems cool, even in 3dmark06.

Pic pls, mine also is stock, cut from original one...

[keninishna]

How are you guys determining the voltage on the card for the 4870 the only pic I've seen in this thread is just a general area to try out unless I've missed something I'm going to solder a set of 4 10 ohm fixed resistors together and use that as the mod because I've had experience with vrs moving over time.

[865pe]

4870, VGPU and Pencil mod pic please

[r4st4m4n]

Pictures 2 pages before: http://www.xtremesystems.org/forums/...&postcount=352

Below for the VR values.

I was out, I Have PMed the values to him but he was not responding.

VDDC 50 ohm

the mem mods should be 5k each.

Not sure if it has been 100% confirmed though

[Skauneboy]

To avoid the resistance getting too low I plan on using a 25-turn 100ohm trimpot connected to a fixed 8.2ohm resistor. Does it matter what wattage rating the fixed resistor has? I can get 0.25W, 0.6W 1W or 5W. The higher the better?

[Clemmaster]

1W is high enough in every cases, don't worry for this. And I assume it is 1w with poor working conditions, which you won't have on your card

[diablos]

THETA
Can you post a real photo of your vmod?

[CCC]

from MMouse

[keninishna]

from MMouse

...

Sexy I knew they could hit 1ghz I bet he could get some more on it too. Do you know his volts?

[SNiiPE_DoGG]

How are you guys determining the voltage on the card for the 4870 the only pic I've seen in this thread is just a general area to try out unless I've missed something I'm going to solder a set of 4 10 ohm fixed resistors together and use that as the mod because I've had experience with vrs moving over time.

im thinking i will do this too because I can get nice metal oxide resistors at my local shop in 10 ohm, as i will be doing 24/7 at the volt mod and not LN2'ing or anything just a small voltage bump should be fine for me

[overcrash]

Guys can you make a pencil mod for the 4870? I really don't like to void the warranty of the card.

[diablos]

Guys can you make a pencil mod for the 4870? I really don't like to void the warranty of the card.

pencil is not good
for warranty: if you remove the mod and clean the vga you will havan't problem

[Hazzan]

@CCC : only one words " AMAZING " keep pushing it .....realy nice jobs Man..

[quake6]

@CCC: Really good score,keep pushing... Can you try 05,06 vantage maybe?