7900GT over voltage protection?

[t024484]

So...after having the 50kohm resistance connected instead of the stock 5kohms if we connect the ISL6568 21pin to ground we will read on the vgpu measuring point 1,7v am i right ?

So without removing the 5kohm we can have 1,5v max...after replacing it by 50kohms we can raise till 1,7v ?

Yes, although I am pretty sure that with 1.7 Volt we will have to adjust the Current limiter.
This is the 3.5Kohm resistor from pin 10 to pin 11.

[t024484]

I can see in the 7900GT picture on this thread page1 that pins 22, 21, 30 31 and 32 go somewhere else, meaning that the current 1.2V on the 7900GT is not hardwired.

Does anybody have a clue of where those pins are going? GPU?

No it is not hardwired.
The traces are going to ground or via a resistor to +5Volt I suppose, in order to get a 0 or a 1.

[s e t h]

i made a pretty picture

i did none of this. all credit to the developers

[t024484]

i made a pretty picture

i did none of this. all credit to the developers

There are two possibilities:
1) Either you do not change any resistor at all, and then this table applies:

options starting at 1.200 Volt with the existing sertting of "01110"
-------1.200-1.250-1.300-1.350-1.400-1.450-1.500-1.550

Pin22----0-----0----0------0------0-----0------0----0
pin21----1-----1----1------1------0-----0------0----0
pin30----1-----1----0------0------1-----1------0----0
pin31----1-----0----1------0------1-----0------1----0
pin32----0-----0----0------0------0-----0------0----0


2)Or you change the resistor as in the picture from Flytek to 50Kohm,
then this table applies starting from 1.5 Volt for the existing setting of "01110"

-------1.500-1.525-1.550-1.575-1.600-1.625-1.650-1.675-1.700Volt

Pin22----0-----0----0------0------0-----0------0----0-----0
pin21----1-----1----1------1------1-----1------1----0-----0
pin30----1-----1----1------0------0-----0------0----1-----1
pin31----1-----0----0------1------1-----0------0----1-----1
pin32----0-----1----0------1------0-----1------0----1-----0

In the Picture that FLYtek mailed, the wrong combination of resistor and table was made.

[***Deimos***]

Simplified, I removed pin info, diagrams tables etc.

[SF3D]

t024484

Let's make a guide, so everyone can do this. If you add that table in the picture and mark the mod points. It will be easier to understand, if someone haven't read this thread before.

[SF3D]

***Deimos*** did it already! Thank's

[LardArse]

ingenius!
after doing the 50k mod, (must do before this) this should be the 1.6 and 1.7v mod. but let me test it out 1st. prolly need the ocp mod 1st too

[Nosfer@tu]

Just so DAMM small to solder.

and the ISL is very exposed to the heat+it being so complicated makes i more likly to kill the chip when soldering maybee?

[t024484]

***Deimos
Simplified, I removed pin info, diagrams tables etc.

That's the whole story.
Well done Deimos
The info from LardArse should also be used because this makes it a lot easier to solder.

[Chr0n1c]

Just so DAMM small to solder.

and the ISL is very exposed to the heat+it being so complicated makes i more likly to kill the chip when soldering maybee?

It is extremely small, seems the easiest way is to just mod the resistor and stick with 1.5v

[***Deimos***]

The easiest way would be to stick one end of wire right between ground and pins #30 and #31, and get +0.25V.

With such small places to solder, its difficult to get one exact pin. But this way, its easier.. 1.2-1.45V made easy.

[TimeOut]

Can we do the pencil trick between pin 21 and 22?

This should set 1.4V VGPU right away.

[Ebola]

Congratulation men, you did it.

Did anyone check where via lead on the other side of the PCB, because soldering directly on ISL legs sounds quite hard.

Is 1.5V and higher not too high for the regulator embedded on the GT ? (that are different from GTX )

[Hugo van Dijk]

So this is correct right (just asking to be sure)? to get 1.5V

[Chr0n1c]

The easiest way would be to stick one end of wire right between pins #30 and #31, and get +0.15V.

With such small places to solder, its difficult to get one exact pin. But this way, its easier.. 1.2-1.35V made easy.

Oh I like that!

[TimeOut]

The easiest way would be to stick one end of wire right between pins #30 and #31, and get +0.15V.

With such small places to solder, its difficult to get one exact pin. But this way, its easier.. 1.2-1.35V made easy.

You do the same with pins #21 and #22 and get +0.20V or 1.40V VGPU

[afireinside]

ingenius!
after doing the 50k mod, (must do before this) this should be the 1.6 and 1.7v mod. but let me test it out 1st. prolly need the ocp mod 1st too

So that's for vgpu, then just replace the resistor with a 50k and ground it to pin 21? I may get a GT now...

[Chr0n1c]

You do the same with pins #21 and #22 and get +0.20V or 1.40V VGPU

Err seriously? That simple?

[tranceaddict]

Can we do the pencil trick between pin 21 and 22?

This should set 1.4V VGPU right away.

I want to know as well, as my 7900gt is on its way and I already have a NV Silencer 5 for it. However, I can't solder for the life of me and I want a simple volt mod that does not require any skill.

[Belarnion]

Congratulation men, you did it.

Did anyone check where via lead on the other side of the PCB, because soldering directly on ISL legs sounds quite hard.

Is 1.5V and higher not too high for the regulator embedded on the GT ? (that are different from GTX )

I'm afraid it won't be much easier...



BUT: If Pin 32 and pin 22 is *already* '0', why not just connect
Only pin 32 to pin 30 and 31 to get 1,350V or
Only pin 22 to pin 21 to get 1,4V or
pin 32 to pin 30 and 31 AND pin 22 to pin 21 to get 1,55V

Would that work?

[VoRtAn_MaDgE]

If you guys encounter problems soldering those tiny legs of the intersil chip just isolate the closests legs near the one to solder with seal string for example...

[majestik]

Anyone thought of using a DIP switch?

[^don.k's^]

Also you can search for the same point in other PCB location, checking continuity between it and the pin you search for. Do you understand what i mean ? ( im not sure of the words to use )

[***Deimos***]

Can we do the pencil trick between pin 21 and 22?

This should set 1.4V VGPU right away.

I think this would work.
But, getting pencil in there is just as difficult as soldering.