Accepted Shares / OS X / cgminer

[ralfr]

Absolutely new to Bitcoin aspens got a couple of questions:

- I set up cgminer on an iMac, a MacBook Pro and a Mac mini.
- I'm using the btcguild.com pool.

On the iMac and Mac mini, cgminer reports it cannot use any GPU. On the MacBook Pro it reports using 2 GPUs.

Question 1: Why is this so? Do iMacs and Mac minis not have "qualifying" GPUs?

In BTC Guild dashboard I see all three workers, however, the "Accepted Shares" column for the iMac and Mac mini workers report 0 while the MacBook Pro worker says 50.

Question 2: Does this mean that the other two workers don't mine at all?

I'd love to better understand this and thank you for looking into my newbie post.