I want to install a PCI Express add-on card with extra USB 3.0 ports on my ASUS P8Z77-V LX motherboard, but I'm confused about how PCI Express works.
Right now my graphics card is in a PCI Express 3.0 x16 slot. Below that I have another PCI Express slot. The manual describes it as: "PCI Express 2.0 x16 slot (black at x4 mode, compatible with PCIe x1 and x4 devies [sic])." I want to put the add-on card into this slot. The add-on cards I'm looking at are all x1.
I've read that using multiple PCI Express slots can negatively impact the performance of other components in other PCI Express slots. How do I know if this is going to happen? Will installing this USB add-on card in the PCI Express 2.0 x16 slot decrease the performance of my graphics card in the PCI Express 3.0 x16 slot above it by forcing it to use less lanes and therefore run at a lower speed? Once I have it installed is there some way to test and find out if the graphics card's x16 slot is currently running at x1, x4, x8, or x16?
Also, I see that most of these cards come with a 5V 4-Pin power connector. Is this necessary if I'm hooking up devices that their own power supplies (like external hard drives with their own power cords)? Does using the power connector have any impact on the card's speed or other capabilities?
One final question, as far as I can tell all of these USB 3.0 add-on cards are made for PCI Express 1x slots. Is there a reason for this? Couldn't multiple USB 3.0 ports move enough data to bump into the PCI Express 2.0 x1 limit? Wouldn't a card with 4 USB 3.0 ports benefit from PCI Express 2.0 x4, x8, or x16?