i got 30 chips, should i order 10+20 or 10+10+10? is there a downside with either?
The 10 chip version may give you higher overclocks (>450mhz) because there is extra headroom on the regulators (20 chips at 450 is nearing max current of board). It'll probably get lower temps too. But it'll cost more.
Of course its open if you can go much higher at all.