How do Nvidia limit overclocks? you have to draw the line at max voltage requirements some where, as said you have well enough leeway with Nvidia volts to get a massive overclock, what would you need any more volts for that would probably flake out the core anyway, point is ATI limit overclocking drastically through the bios and Nvidia do not, for what reason?
Nvidia GTX 460 - max voltage allowed 1.087v
ATI HD 5000 - max voltage allowed = 1.35v.
ATI HD 5770 / 5850 / 5870 on air - around 1000 Mhz easilly possible out of the box with an unlocked version (MSI or Asus).
Nvidia GTX 460 - Around 800 - 900 Mhz possible out of the box, and to reach the higher limits you have to get a really lucky chip.
I have to disagree, you dont get anywhere near enough leeway with Nvidias stock limits, and ATIs limits are nowhere near as drastic as Nvidias are (providing that you buy a pre unlocked version, which is what you should do if you plan to overclock).
As with my MSI 460s, they are at 78 degrees at max load, 890 Mhz, 1.087v, which while I am happy with, I hardly believe they would 'flake out' if set any higher. If you mean that your GTX 480 would flake out, then yes it would because thats not a very efficient or overclock friendly card in the first place.
Can any of the current Nvidia cards even be clocked as high as ATIs on air? No they cant.
Example, all 5870's apart from specialist brands like Asus and MSI have their overclocks limited to 900Mhz which is a measly 50Mhz over the stock clocks.
You want to know the easiest solution to this? Simply buy either the Asus or MSI version if you want to overclock them. Its not that difficult.
You can see me often blaming cards that took off the voltage tweaking altogether, and even ones that come with poor cooling, but individual brands of cards are not to blame for the actual GPU company. If you do want to overclock, buy a card from an AIB that supports overclocking. That really is the best thing to do.