crossfirex mobos with only 1 pcie 16x slot... pointless? (n00b here)

lookin to put together a new pc after not paying attention to new technology for about 7+ yrs.

I am intrigued by the whole sli/crossfirex multi gpu concept, and stumbled across many mobos, such as this http://www.asus.com/products.aspx? [...] odelmenu=2, which only has 1 pcie 2.0 x16 slot, along with several pcie 1x slots.

doesnt that kindof defeat the purpose of crossfirex? i thought cfx scaled to the lowest clock speed/GPU clock, memory clock, and video RAM size of all available cards. i dont even know how the pcie slot bus link factors into this (or even if thats the correct terminology).

my point being, with only 1 16x slot, a second vid card would have to go into the pcie 1x slot. i have to think a vid card that is only 1x capable would severely limit the performance of the first card, or wouldnt contribute much at all to overall performance.