PCI-Express Physical vs. Electrical - what?

[Randybob]

Something that's had me confused of late is motherboards that claim to have two PCI-Express x16 slots, but one of them is only 4x or 1x electrical. Why do they even call it an x16 slot then? Why don't they just call the slot by the speed it actually functions at?

 

[myocardia]

Because an 8x/16x PCI-E slot is about 5 times as big as a 1x/4x slot.

 

[Matthias99]

Originally posted by: Randybob
Something that's had me confused of late is motherboards that claim to have two PCI-Express x16 slots, but one of them is only 4x or 1x electrical. Why do they even call it an x16 slot then? Why don't they just call the slot by the speed it actually functions at?

Basically, think of it as a slot that can fit an x16 card, but only runs at x1 or x4 speed.

All PCIe devices, in theory, are supposed to be downwards-compatible to lower speeds (although if the bandwidth of the connection isn't high enough, the device may not work well).

 

[Randybob]

Originally posted by: Matthias99

Originally posted by: Randybob
Something that's had me confused of late is motherboards that claim to have two PCI-Express x16 slots, but one of them is only 4x or 1x electrical. Why do they even call it an x16 slot then? Why don't they just call the slot by the speed it actually functions at?

Basically, think of it as a slot that can fit an x16 card, but only runs at x1 or x4 speed.

All PCIe devices, in theory, are supposed to be downwards-compatible to lower speeds (although if the bandwidth of the connection isn't high enough, the device may not work well).

Why would anyone want a slot that size but goes slower?

 

[Matthias99]

Originally posted by: Randybob
Why would anyone want a slot that size but goes slower?

Why would you want a slot the same speed but that can't take an x16-size card?

You could probably run a PCIe video card for 2D work only in one of these slots -- but you can't put one in an x4-size slot (no matter how hard you try to cram it in there).