SDK 2.1 vs 2.4 - what's the difference?

[bitless]

I keep hearing that the same .cl kernels compiled with SDK 2.1 and 2.4 are giving different MH/sec results, and 2.4 seems to be giving worse results. So... is this true? Presumably, the same source code compiles into different machine code, but does anybody know what exactly is the difference that's causing this?

I have only 2.4 installed... if nobody knows what the difference is, would it be too much to ask somebody to compile phatk's kernel with 2.1 and post the disasm of the code to pastebin or some such? (just copy/paste it from AMD's kernel analyzer, and I dig through the stuff myself)

Thanks a lot!

[Maxim Gladkov]

SDK 2.1 is just faster than 2.4. No other differences for mining...