Question PCIe USB-C card doesn't fit PCIe slot on motherboard ?


May 9, 2012
I have an "ASUSTek COMPUTER INC. PRIME H270-PLUS" MB (as shown exactly from CPU-Z).

The board has these slots:

one PCIe x16 used for an ASUS GTX1080 ROG STRX video card
one PCIe x4 used for another identical ASUS GTX1080 ROG STRX video card
three PCIe x1 expansion slots

i wanted to add usb c (or thunderbolt 3!) support so i recently purchased a
" PCIe USB 3.1 Card - 2X USB C 3.1 Gen 2 10Gbps - PCIe Gen 3 x4 - ASM3142 Chipset - USB Type C PCI Express Card (PEXUSB312C3)"
from amazon:

this does not fit in my mainboard. it is advertised as PCIe, and i have PCIe slot available, but (and this is where my ignorance shows)
from where the "key" (?) is on the connector part of the card, the length of the front half of the controller card is shorter than what is on the MB, and the 2nd half is longer.
if these are indeed BOTH PCIe, why are they different / opposite?

Please note: i have already returned the card to amazon, but i still need to know whats going on so i can make an educated purchase.
Well there was one other alternative. If you were OK with limiting the card to 985MB/s (which is enough to run one port at 3/4 speed) then you could've carefully cracked the back of an x1 slot off to make it open-ended.

Some motherboard manufacturers, most notably ASRock (which was spun off from AsusTek in 2002 to compete against OEM economy brands like ECS or Foxconn) come with open-ended slots as stock.

But with your board it's easiest to just order a x1 card.