ATI 4850/4870 voltmod thread

[dean0]

ok thanks ive soldered the vgpu point just need to ground then ill post some pics and results

[dean0]

i dont think this vgpu mod works for the 4870. Ive done everything correct as in pic execpt i used a heatsink screw for the earth. When im turning the 50k vr there is no change from 1274v, which i had set in bios, any ideas?

[dean0]

Sorry it does work vgpu at 1.3v, i hadnt turn the vr enough how how can i push on stock cooler?

[jimmyz]

i dont think this vgpu mod works for the 4870. Ive done everything correct as in pic execpt i used a heatsink screw for the earth. When im turning the 50k vr there is no change from 1274v, which i had set in bios, any ideas?

where did i say 50k? it is a 50 ohm VR. no wonder you had to crank it way in.

[dean0]

it wont damage card unless i give it too many volts just gota be carful right?

[jimmyz]

it wont damage card unless i give it too many volts just gota be carful right?

exactly, keep an eye on the volts. a 50 ohm will give much better voltage control, more linear. also there should be some sort of ovp if you make a mistake, but I wouldn't count on it.

[dean0]

kk thanks . Would a 5k be better than 50k? i cant seem to find 50ohm vr in my local shop they only have 5k 10k 50k...........
Iam at 1.33v and if i go slightly higher screen goes blank and i have to restart? any ideas

[jimmyz]

kk thanks . Would a 5k be better than 50k? i cant seem to find 50ohm vr in my local shop they only have 5k 10k 50k...........
Iam at 1.33v and if i go slightly higher screen goes blank and i have to restart? any ideas

get a 5k and try it. the 50k has no real scaling a tiny move will probably put you past the OVP limit.

[dean0]

Just found out my local shop sells 1k and 500r. which one is best?

[jimmyz]

lower the better. the 50 ohm was what the other tester (Theta) used.

[Laykun]

Hey Dean, I can't find a 50 at my local store either. Let me know how the 500 works out for you.

[Theta]

Sorry for the delay - was away for the holiday...

You guys will need to order a 50 ohm, they're never in stores...

That being said, you CAN buy a 1k ohm off the shelf at almost any store (including radioshack)... BUT, be very careful, as the 50 ohms you need will me the last 3/4 turn of the 15-turn pot.

Lastly, you can use fixed resistors to get the desired voltage as follows:

10 ohm fixed ~ 1.566v
15 ohm fixed ~ 1.465v
22 ohm fixed ~ 1.400v
27 ohm fixed ~ 1.375v
33 ohm fixed ~ 1.355v

CAUTION - I have not tried anything past 22 ohms (1.4v) on the card. So far, it has lived through all of the other voltages. The mod is successful, but I still need some help with BIOS modding to get some good clock numbers past 790.

[diablos]

Sorry for the delay - was away for the holiday...

You guys will need to order a 50 ohm, they're never in stores...

That being said, you CAN buy a 1k ohm off the shelf at almost any store (including radioshack)... BUT, be very careful, as the 50 ohms you need will me the last 3/4 turn of the 15-turn pot.

Lastly, you can use fixed resistors to get the desired voltage as follows:

10 ohm fixed ~ 1.566v
15 ohm fixed ~ 1.465v
22 ohm fixed ~ 1.400v
27 ohm fixed ~ 1.375v
33 ohm fixed ~ 1.355v

CAUTION - I have not tried anything past 22 ohms (1.4v) on the card. So far, it has lived through all of the other voltages. The mod is successful, but I still need some help with BIOS modding to get some good clock numbers past 790.

try this to pass 790
http://www.overclex.net/data/images/...cktool-9.8.rar

[vengance_01]

Just to give everyone a heads up. Do not use the Zalman VF-900 with a volt modded 4850. Even at 1.21 load it gets very hot to touch. Granted I do have 85F room temp. But The AC S1 passive with good case airflow is beating the Zalman. under 60C full load. I don't have room for fans, but I will try to add them.

[Theta]

Just to give everyone a heads up. Do not use the Zalman VF-900 with a volt modded 4850. Even at 1.21 load it gets very hot to touch. Granted I do have 85F room temp. But The AC S1 passive with good case airflow is beating the Zalman. under 60C full load. I don't have room for fans, but I will try to add them.

Now I did warn you!

Just had to say it.

[0maro]

Why zalman vf-900 is so bad for modded 4850?I don't understand that..

[Theta]

Why zalman vf-900 is so bad for modded 4850?I don't understand that..

Not beefy enough to dump the heat effectively.

After 1.25v went into free climb 90+C in our tests.

[vengance_01]

Now I did warn you!

Just had to say it.

I know you did, but I just had to find out. I just can't believe how well the S1 handles this card passive with great airflow in my case. I have room for 2 80mm fans even with a small wireless card in my way. Gonna rig those up as well. But man I love this card. Playing Crysis at 1680x1050 and a popular custom config. Everything looks so good and now very playable. Should get a nice boost once I go for 750 again. I am glad I got the 4850. But what I don't understand is how ATI could ship the 4850 with the bios it had and how hot it was running. I remember how much heat the card at stock was dumping into my case. It was terrible.

You will be seeing my old 8800GT and G92 GTS in the FS section soon. =)

[adpr_02]

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. Working on a beefy ramsink right now. Time to push to 1000mhz.

[dean0]

Big probelm! I done the vgpu mod succesfully and after testing stability in atitools artifact scanner it looked good but know when i run 3dmark06 my frames have dropped and i have loads of artifacts, its the same in crysis.
I did at one point boot with the volts at 1.7v could this have buggered the card? ow well back to the shop for a new one

[jimmyz]

Big probelm! I done the vgpu mod succesfully and after testing stability in atitools artifact scanner it looked good but know when i run 3dmark06 my frames have dropped and i have loads of artifacts, its the same in crysis.
I did at one point boot with the volts at 1.7v could this have buggered the card? ow well back to the shop for a new one

try driver re-install too.

[dean0]

just tried driver intall, still lots of artifacts on games and 3dmark, you think to many vol;ts?

[vengance_01]

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. Working on a beefy ramsink right now. Time to push to 1000mhz.

on the 4870 or 4850?

[W1zzard]

just tried driver intall, still lots of artifacts on games and 3dmark, you think to many vol;ts?

did you have time to measure how much current flows across your resistor? with only 50 ohms i could imagine it getting quite big

[jimmyz]

did you have time to measure how much current flows across your resistor? with only 50 ohms i could imagine it getting quite big

He used a 50K VR for his mod at first had to screw it all the way in to make voltage climb.