a PCIe card will physically fit (and work correctly) in any slot that is at least as large as it is (e.g. an x1 sized card will work in any sized slot);
In both cases, PCIe will negotiate the highest mutually supported number of lanes.
The manual i got with my XFX 780i motherboard says this...
PCI Express x1 Slot
There is one PCI Express x1 slot that is designed to accommodate less
bandwidth-intensive cards, such as a modem or LAN card. The x1 slot provides
250 MB/sec bandwidth.
PCI Express x16 Slots
These three PCI Express x16 slots are reserved for graphics or video cards. The
bandwidth of the x16 slot is up to 4GB/sec (8GB/sec concurrent). The design
of this motherboard supports three PCI-Express graphics cards using
NVIDIA%u2019s SLI technology with multiple displays.
When installing a PCI Express x16 card, be sure the retention clip snaps and
locks the card into place. If the card is not seated properly, it could cause a
short across the pins. Secure the card%u2019s metal bracket to the chassis back panel
with the screw used to hold the blank cover.
So they appear to be comflicting, has anyone actually done this ? did it work? is there anything i can do?
please help me with both problems I will read back here before i continue my build later today.
I have a CM Stacker 830 evo so atleast I will have the 4 side panel fans bringing in air to help cool the cards, and the overall case. In addition to that i a fan on the front for intake, and top , and back for outtake.
if i was you i'd switch all fans to outake as in a hot summers day your pc will be in envirostate being equal to the earths temp thus you want all heat exausted and disable fan monitoring bios configurations to off so as fan speeds are maximal overiding airflow at this point is ok aslong as your exaust fans are bigger than your cpufan/gcard fans you will achieve exaustion .120mm front and rear are crucial with side pannel fan , i run a zalman sideblower over corsair heatsinked dominator ram in a thermaltake soprano with 70* bios heat warning