Why would a PCIe x16 slot be limited to PCIe x1 card?

[TylerH]

I have a PCIe x16 slot that came with a cover that has the label "PCIe x1/DVI ✓" and "PCIe x4/x8/x16 ☓" which I interpreted to mean that it supports PCIe x1 and not x4/x8/x16. This is corroborated by the fact that the cover leaves the exact shape of a x1 slot, covering the rest. The cover is easily removed, which is exactly what I plan to do, since PCIe is lane based and I'm okay with running a x16 GPU on one lane. My question is more out of curiosity, why would the put a x16 slot on the board, but only use one lane.

To be a little more specific, it isn't build into the board. It's a PCIe x16 card that plugs into the board vertically, and has the aforementioned x16(that is really an x1) slot and a PCI slot extending horizontally from it.

Pics attached, one w/ cover, one w/o.

 

[JaredJames]

I have a PCIe x16 slot that came with a cover that has the label "PCIe x1/DVI ✓" and "PCIe x4/x8/x16 ☓" which I interpreted to mean that it supports PCIe x1 and not x4/x8/x16. This is corroborated by the fact that the cover leaves the exact shape of a x1 slot, covering the rest. The cover is easily removed, which is exactly what I plan to do, since PCIe is lane based and I'm okay with running a x16 GPU on one lane. My question is more out of curiosity, why would the put a x16 slot on the board, but only use one lane.

To be a little more specific, it isn't build into the board. It's a PCIe x16 card that plugs into the board vertically, and has the aforementioned x16(that is really an x1) slot and a PCI slot extending horizontally from it.

Pics attached, one w/ cover, one w/o.

I have no idea, but at a guess I'd assume it's for the same reason most car manufacturers only use one template for the dashboard. For example, your dashboard will have all the necessary holes for buttons (air conditioning etc) but on a model of the car that doesn't have AC it is simply blanked off.

This allows you to use one manufacturing process for every model, but only install the relevant tech on the models that need it. Cost reduction.

In your case, you'll probably find there are a number of versions of the card. Yours is a model that only supports x1 but there is another model that is identical but takes the rest. For yours they simply blank it off instead of having to build a separate card for x1 only.

That, or I'd say it's to allow people to do what you want to do. Plug in an x16 card but run it on x1.

 

[TylerH]

I had assumed it was to allow room for both the PCI and PCIe x1 to run though the same card. Is it likely that the slot the expansion card plugs into(the slot that is actually on the mobo) is of a higher lane count than 1?

 

[TylerH]

I went ahead and tried it, and there's a problem. If I try to boot with the x16 card in, it reboots, and refuses to boot. I get an "extended block move" error, which, from what I can gather, means there's an address conflict. Is it possible that an x16 would cause a problem, whereas an x1 wouldn't? If so, would it be likely that putting some tape on the rest of the card, all but that used by x1, would mess it up?

 

[LudusRex]

There could be a few reasons why a PCIe x16 slot would be limited to a PCIe x1 card. One possibility is that the manufacturer designed the slot to be versatile and accommodate multiple types of cards, including PCIe x1 and x16. This allows for more flexibility for users who may need to use different types of cards in the same slot.

Another reason could be cost-saving measures. PCIe x1 cards are typically less expensive than x16 cards, so by limiting the slot to x1, the manufacturer may be able to offer a more affordable option for users who do not need the full bandwidth of a x16 card.

It's also possible that the PCIe x16 slot is not actually limited to a x1 card, but rather the cover is misleading. It's common for manufacturers to use multi-purpose covers that can accommodate different types of cards, but only have one label on them. In this case, the cover may only have the label for PCIe x1, but the slot itself may still support x4, x8, or x16 cards.

Ultimately, the reason for the limitation would depend on the specific design and purpose of the motherboard. Without more information, it's difficult to determine the exact reason for the limitation. However, as a scientist, it's important to understand that design decisions are often based on a variety of factors, and there may not always be a clear or straightforward answer.