One thing is that 16X can be 16X or 8X or 4X or 1X depending on how you adjust bios. Because PCI-e was invented by Intel & then dropped from Intels developement, those redundand specialty slots, 1X, 4X never had much developement, pci has 1X & 4X capabilities in most machines.
Worse, 16X slot(s) often turned out to be only 8X, due to improper engineering. Today you can get 16X slot(s), yet then you need game card with 16 or 32 or 48 lanes to fill space. Thats todays top & its not Vista friendly, designed at time prior to Vista. So new level of game cards is coming 16X/32X. with twice bandwidth of todays top game card(s). Unfortuneately 4 16X slots will not take four 48 lane game cards & do any more than one 48 lane game card, theres just not enough bandwidth to support anymore than 48 lanes at present. So new slot or slot with greater bandwidth or more slots or just get ripped off by advertiseing. By summer mess will be in full swing.
This is why 1X slot goes relatively unsupoorted, theres just not time to figure out such short lived & difficult design. When same result can be reached with pci 1x/4x slot that already is mature.
For instance how to double 16X slot bandwidth without affecting 1X slot bandwidth, probably not possible. Then ther'd be next generation of one X too, too confusing for average consumer. So PCI-e 2.0, or 16x/32x like 2x/4x pci (agp) years ago or no solution, which leaves all 3d '6 scores with no improvement & then games exact same size even though game card is twice as fast, well room to profit is from others confusion & thats where its all leading. Its best to fill all slots, 1X using firewire card may be best idea, as its HOT & makes your system smoother & hotter, even if it remains unused, once installed.
Signed:PHYSICIAN THOMAS STEWART VON DRASHEK M.D.