Replacing GPU with another

[gepal]

Hi there, AFAIK this is my first post to this forum. Because I couldn't find info on this topic so I started new one.

Recently I've got falcon mobo with poopcorned GPU and found GPU replacement on ebay, BUT!, these replacements have different numbers and component placement on GPU.
I guess that GPU's from ebay will be from older consoles than I have, so I assume that these chips will be 90nm (as in falcon). The question is following:

Does anybody have any experience of replacing GPU with different numbers ? Or in other words, should I look for exact parts, or these replacements will be good ?

The blown chip: http://img42.imageshack.us/img42/6162/img5486d.jpg

[Arakon]

they won't work. all other issues aside, they have a higher current draw, and the console can not supply that.

[ddxcb]

thats look like the motherboard is shot dude srry

[B1N4RY]

What exactly is that brown stuff anyways?  I have several scrapped motherboard at my place that are covered with that crap after the previous user failed to reflow the GPU?

[Arakon]

I'd say flux, or in case of extreme heat, the pcb laquer.

[mushy408]

Looks like flux residue... and cooked

[B1N4RY]

I doubt it is flux...
I tried to reflow a dead Xbox motherboard looked like that, and more of that black stuff will continuously flow out, and is very sticky. As Arakon suggested, it is probably the PCB lacquer due to extreme heat caused from improper reflow. What ever it really is, it's not good.