I've been monitoring my hashing and shares more closely and it sort of dawned on me that Mhash does not necessarily translate into a share. More clearly, X Mhash does not guarantee Y amount of shares within Z amount of time. Is this correct?
example only: 100Mhash equals 1 share every second. So 1 minute would always yield 60 shares
I've noticed some rounds, let's say under 2 minutes, I was not able to able to get any shares submitted. But another, under 1 minute, I was able to get 6 shares submitted.
It takes on average 2^32 hashes to get a share. So it takes roughly 10 seconds to generate a share on a 6970 (420MH/s). This is a random process, so it will vary, but over the long term, it should average to 2^32 hashes per share. So it would take about 4.2GH/s to average 60 shares per minute.
It will take on average "difficulty" number of shares to generate a block.
See this for more:
https://en.bitcoin.it/wiki/Difficulty#How_soon_might_I_expect_to_generate_a_block.3F