speaker connection

I feel like a noob for asking this question, but I can't find answer on the web.

My 5.1 speakers have 3 connectors 1st for central/subwoofer, 2nd for front left/right and 3rd for back left/right. I suspect all of them are analog.

I am thinking about upgrading my computer, so my question is if all 5.1 and 7.1 mobos and soundcards support this configuration. Or are there cards that do not support it?

But the cards that are 7.1, do they support the same connection for 5.1 speakers?

Almost certainly - the 7.1 sound cards that use one connector for Surround L & R and Surround Back L & R simply get their data from extra poles on the plug itself (cummon with Creative brand Speakers and sound cards) - 5.1 speakers do not posses these extra poles on the plug so it will function without any problems - just ensure you set the speaker setup to 5.1 in the soundcard's software.