Will a pcie 2.1 x16 run in a pcie xi6 slot

[bazilbrush57]

can i use a pcie 2.1 x 16 or 2.0 x16 in a pcie x 16 slot

 

[akxpckwb]

Yes. PCI-e are backwards compatible

 

[Gman450]

The PCI-E slots are backwards compatible, but there will be a problem regarding bandwidth.
Also, do you mean a PCI-E 1.0 or a 1.1 X 16?