Gouli - That's interesting and could explain a lot. One will look for some drivers. It may all become academic since it's still 'updating'.
yellowtriumph That's also interesting. I'd wondered about that pad's efficiency. As mentioned, a forum member, talking about cleaning and reapplying the gold compound, said if the metal was perfectly smooth there wouldn't be any need to apply it, so all we're trying to do is compensate for the unevenness of the surfaces. He put a 3mm blob in the middle of a round heat-fan and said it would spread out. (Intel i5) I used the spatula spreading method, but did it thinner than usual.
Back to the grey stuff. Back then, 3 years or so, folk were putting copper coins on the video chip. Real old copper ones, I hope.
The chip as you may know is the one at 45 degrees and the daughter board is stuck with a red goo as a fix for their balling failures. That stuff was so hard I couldn't cut it, or melt it with an iron. But I think they used a bit of imagination if they thought that would compensate for balls that hadn't flowed. They would be - and were on most failures - just like any other bad joint after a year or so.
When I read the BIOS going by I assumed I'd had some success and took great care with the proper rebuild. It was then that I found I was out of luck.
A local chap here - I'm in Essex - claims some success with Coke tin shields and a heat gun. A plasterer by day, he seems to have a good reputation.
I'm totally at a loss as to how the re-balling works. They seemed to just clean up and sprinkle .6mm balls into the space and then shove them about with a brush. I can not imagine any other way than to stick them with flux and register every ball with NOT ONE TOO MANY! The heat gun was obviously very expensive kit but the timing was just waiting for the chip to 'drop'. Very odd way to save money in manufacture.