no, that's not true. If you're running Vista 64 bit it's all good. If you're running 32 bit Vista it might recognise the full 8 gig but it will not use more than 3.5 or so.
As far as I know all Phenoms can address something like 128 GB.. or was it 64, don't remember. It's a lot more than 8GB at least, that I know for sure
It's the OS and motherboard that sets the limit really.
Cooler Master HAF 932 Full Tower : Corsair 750HX Modular PSU : Asus Crosshair III Formula : Phenom II X4 965 125W
Corsair H-50 CPU Cooler : Corsair Dominator GT DDR3 1600 7-7-7-20-1T 2x2GB : WD Caviar Black 32MB 640GB : Sapphire HD5870 Vapor-X
Antec Fusion Remote Black : ASUS M4A785TD-M EVO : Athlon II X2 240e : Crucial BallistiX 1600 2GB x2
Corsair 400W : Sapphire Radeon HD6850 : Lite-On iHBS112 BD-Burner : WD Caviar Green 500 GB