Joey Gadget’s reports that the new Xbox 360 models are fitted with new 'Jasper' motherboards as well as a new and improved graphics chip that fixes the “Red Ring of Death (RRoD)”. The upgraded components are smaller and emit less heat, which in turn should mean no more red lights on your 360.
The problem behind the infamous 360 hardware failures, which cost Microsoft $1 billion in warranty extensions, has never been officially disclosed. According to Gartner analyst Bryan Lewis though, the defect was down to Microsoft's decision to manufacture the 360's graphic chip itself, rather than paying a third party.
If you're keen to find one of the new 'Jasper' 360s, you should look for a manufacturing date as early as June 8, 2008, 'Lot 8031' and up, and 'Team CSON' on the back of the console - though you'll probably have to bribe the bloke behind the counter to see it.