Like you said 'luck'. That is all you could rely on.
I see. I'm not very good at maths. Is it impossible to quantify the likelihood of 100 hd5850's finding a block? Or just totally random?
https://en.bitcoin.it/wiki/Difficulty#How_soon_might_I_expect_to_generate_a_block.3F
Thanks.
difficulty * 2**32 / hashrate
how do you calculate 2**32
what does the double ** mean?