G84 = 8400
G86 = 8600
I was thinking it was one of those chips that are known to be defective, but since it's not..
I'd say you got a bad 7400. Sony isn't known for quality parts.
Machine is 4 years old and has been working fine, I got it 1 week ago as a dud, not had back off yet, it looks interesting, don't want to spend a day with it in bits to find it needs a motherboard, I was looking for a ribbon cable out or a dud daughterboard and to make sure that I am going in the right direction, looks like I will be living with the Intel GPU, will keep checking this thread, thanks anyway.