More Cuda cores, too. Nvidia used top-binned dies to enable all those cores, and charged accordingly. I'm yet to find a Vista-compatible app that uses all 12 gigs, btw.
Trivia: That's how at least half of them go. When a MOSFET dies, it usually forms a dead short, so the GPU gets a blast of straight 12V instead of 1.small_changeV it usually gets. Shocked and appalled, it, in turn, also shorts. Now the PSU is dumping 12V into a dead short, basically. Whatever offers the most resistance (the MOSFET itself usually, though in your case the 6+2 connector, which was probably making iffy contact) starts to burn -- itself & everything around it (see pic attached)
BTW, a good percentage of high-end cards from around that time have been mining, so the odds of getting one on its last legs are reasonably high. The first thing i do after scoring a card is try to overclock it -- if a Maxwell card is stable @ +100MHz on the cores & ~+500MHz memory, it's got life left. If not ...i got stuck with many of those.