You can still mine Premine; when you transfer coins from your wallet you pay a transaction fee. This small transaction fee ends up in new blocks on the network. The more people who transfer Premine and the busier the network = the higher the block rewards.
I saw block rewards of up to 1 PMC per block yesterday. It's normally lower than that but it depends on how many transactions are in each block. Best thing to do is just aim some ASICs at it and wait until the network gets busy again.
Ahh okay. So it's SHA256 algo, isn't it?
That explains the diff
Did that fact get removed from the OP?
I might be blind (you know, cause I'm sleepless and sometimes veeeery tired) but I can't see any info about it in the OP.