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PCIe-2.0 x16 (x4 mode) Scaling Bandwidth Ratio

Last response: in Motherboards
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July 10, 2014 9:17:15 PM

Hi, I'm using an Asus P6T MB, and I have a general question.

I have a capture card that needs a PCIe-2.0 x1 slot; I think that I'm going to have to move it into the PCIe-2.0 x16 (x4 mode) slot on the MB to make room for another device.

I know that an x4-mode slot only uses one-fourth of the bandwidth of a "true" x16 slot.

My Question:
Does that bandwidth usage remain constant, regardless of the size of the device that is using the slot? Basically, I'm wondering if my x1 device would only be getting access to the bandwidth of a hypothetical x1/4 slot (based on the ratio of 4 to 16) or if it would simply have access to the bandwidth of a hypothetical x4 slot.

All tips are appreciated.
a b Ĉ ASUS
a b V Motherboard
July 10, 2014 9:26:05 PM

bandwidth is limited by the slowest side

since your card is pcie 2.0 x1, you're limited to pcie 2.0 x1 in the pcie 2.,0 x4 slot
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a b V Motherboard
July 10, 2014 9:38:25 PM

If I understand what you are asking, then the answer is that you are going to get x1 out of that x4. Basically, the PCIe 2.0 x16 slot which only runs at x4 has the rest of the pins (the other x12) disabled. It is basically like a x4 slot with dummy pins so you can fit x16 cards in it. You won't be getting 1/4th of x1 if that is what you were worried about.
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July 11, 2014 8:56:54 AM

...awesome. Thanks guys. You answered my question.
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