Pci Express X16 Slots
Pcie 3.0 X16 Slot
Pcie X8 In X16 Slot

In a previous blog post, we covered the difference between PCI and PCI-X. The response to the post was enthusiastic, and we were asked to write a complementary post explaining the difference between PCIe x1, x4, x8, x16. We are always happy to answer customers’ questions (feel free to contact us with your questions regarding industrial computers).

I removed it, installed on my older Z87K motherboard and it boots no problem with PCI-E 3.0 @ x16 in GPU-Z. I'm trying to think that it's either a BIOS issue or the mobo PCI-E slot failed somehow. I know for sure it was running at x16, but all of a sudden after going from 0505 to 0802 it just defauled to x8. A physical PCIe x16 slot can accommodate a x1, x4, x8, or x16 card, and can run a x16 card at x16, x8, x4, or x1. A PCIe x8 slot can accommodate a x1 or x4 or x8 card but cannot fit a x16 card. Just to confuse the matter further, there are different versions of PCIe interface. It’s also possible that a motherboard may have multiple slot sizes and also different PCIe versions: 1.0a. GPU not in the top PCI-E x16 slot. The first thing to do is to check whether you have the graphics card is installed in the first PCI-E x16 slot, because if you have two or more than one PCIs x16 slots then in most of the motherboards, the first PCIe x16 slot runs at maximum PCIe bandwidth, which is x16, while the second PCI-E x16 slot runs at x8 speed only. Check if CPU, GPU & Motherboard supports PCIe x16. PCIe cards can always operate in PCIe slots with the same or more lanes than the card. For example, an x8 card can operate in a slot with x8, x16, or x32 lanes. Similarly, an x1 card can operate in any PCIe slot. Caveat: Sometimes, a PCIe slot operates with fewer data lanes than the mechanical slot-type indicates. Upgrading your PC with a new graphics card is easy, then, assuming your PC actually has a PCIe x16 slot. If it doesn't, we recommend forgetting about upgrading just your graphics card.

The short answer is:

‘PCIe x1’ connections have one data lane
‘PCIe x4’ connections have four data lanes
‘PCIe x8’ connections have eight data lanes
‘PCIe x16’ connections have sixteen data lanes

The long answer:

Pci Express X16 Slots

The more data lanes in a connection, the more bandwidth between the card and the host. However, there is usually a cost increase incurred with higher lane counts.

PCIe is an updated version of the PCI protocol. Similar to PCI/PCI-X interfaces, PCIe was developed for peripheral component interconnection. PCIe differs from PCI/PCI-X in several ways, but this blog won’t cover most of those differences. However, one key difference will allow us to better understand the differences between the variations of the PCIe protocol (x1, x4, x8, x16 and x32). That key difference is ‘parallel’ versus ‘serial’ data transmission.

In PCI and PCI-X architecture, all of the cards share parallel data lines to and from the host. Differences between card-speeds and slot-types regularly result in throttled data speeds.

In the PCIe architecture, Each card has it’s own dedicated serial data connections (lanes) to the host. This allows each card connection to achieve a bandwidth independent of other cards that may be active in the system. The number of lanes are indicated by the suffix of the PCIe protocol (×1, ×4, ×8, ×16, ×32). Each lane is capable of speeds from 250-1969 MB/s, depending on the version of the PCIe protocol (v1.x, v2.x, v3.0, v4.0).

Pcie 3.0 X16 Slot

PCIe cards can always operate in PCIe slots with the same or more lanes than the card. For example, an x8 card can operate in a slot with x8, x16, or x32 lanes. Similarly, an x1 card can operate in any PCIe slot.

caveat:

Pcie X8 In X16 Slot

Sometimes, a PCIe slot operates with fewer data lanes than the mechanical slot-type indicates. For example, sometimes a motherboard manufacturer will use an x16 mechanical slot even though the data connection is only x8. In these cases, the higher-bandwidth card still may work (for example, an x16 card in an x16 slot with only x8 connection), if the card doesn’t require that extra bandwidth. The following image shows the PCI connections of the motherboard used in DuroPC’s RAC355. Notice ‘SLOT 1/5’ are PCIe x16 slots but only have an x8 connection. Similarly, notice how ‘SLOT 7’ uses an x8 slot but only has an x4 connection. (Click the image to see a larger version.)

X16 Graphics Slot Mean