I need help about 'coasters'.

[Qwerty]

I'm planning on buying a cdrw and the main thing which troubles me is 'buffer underrun' (coasters). I wanted to know what it does how U can avoid this without special protection (JustLink, BurnProof, ect)?
And does this protection really helps?

I found a pretty cheap LG writer, it has 8mg but no buffer underrun protection. Should I buy it?

Oh, and another question, if u know anything about it:
Are these buffer underrun protection are hardware or software (firmware)?

ThankALot, Micheal.