Questions about PCIe x16 video card slot compatibility

[Genyosha]

Do PCIe X16 video cards physically "fit" into x4 or x8 slots?

I was under the impression that the cards wouldn't physically fit into the slot, but I've come across multiple sites that contain articles of video cards going into x8 and x4 slots (non-SLI operation).
[http://www.gamepc.com/labs/view_cont...okie%5Ftest=1]

Basically I have Dell PowerEdge 1420SC server, which contains a x8 slot, and I'd rather use up that x8 slot for graphics (If possible) than use up a PCI slot for graphics.

Thanks

[ImaNihilist]

Do PCIe X16 video cards physically "fit" into x4 or x8 slots?

No. It will not fit. PCIe x16 is the largest physical connector. However, it is possible to put a PCIe x1, x4, or x8 into a PCIe x16 slot.

I suppose it's possible that some PCIe x16 graphics cards that don't actually need the bandwidth could use a PCIe x8 slot if the physical connection is PCIe x8.

[MrDigital]

No. It will not fit. PCIe x16 is the largest physical connector. However, it is possible to put a PCIe x1, x4, or x8 into a PCIe x16 slot.

I suppose it's possible that some PCIe x16 graphics cards that don't actually need the bandwidth could use a PCIe x8 slot if the physical connection is PCIe x8.

The question then is this: How is GamePC running an x16 card in an x8 slot? I know at one point Dell's x8 slots could be filed down to allow an x16 card to "fit" in the slot and work fine, since x16 provides so much bandwidth it's not even funny. Cards don't even utilize AGP8x let alone PCI-E x8. Keep in mind that every lane of PCI-E is 312.5MB/s, so an x8 slot is 2.5GB/s (in both directions). AGP 8x is only like 2.1GB/s (in one direction).

There's no logical reason to need an x16 slot other than the the physical differences of the slots, IMO.

I'd be curious to find out how it all works.

-MrD

[James]

I think all slots should be physical 16x slots. That way, whether you need a 1x, 2x, 4x, 8x, or 16x bus, all cards will fit in all slots.

It's the reason I want a DFI NF4 Ultra-D. That second 16x long slot will be perfect for an 8x long RAID controller.

Man, I wish they would make a 4x RAID controller, but I know it probably won't happen.

All you need is a bus controller that can dynamically allocate the lanes to whichever physical slot needs them.

[Un4given]

The question then is this: How is GamePC running an x16 card in an x8 slot? I know at one point Dell's x8 slots could be filed down to allow an x16 card to "fit" in the slot and work fine, since x16 provides so much bandwidth it's not even funny. Cards don't even utilize AGP8x let alone PCI-E x8. Keep in mind that every lane of PCI-E is 312.5MB/s, so an x8 slot is 2.5GB/s (in both directions). AGP 8x is only like 2.1GB/s (in one direction).

There's no logical reason to need an x16 slot other than the the physical differences of the slots, IMO.

I'd be curious to find out how it all works.

-MrD

I don't think it is a physical 8x slot. It is probably an SLI board. The board only has 16 physical lanes for the PCI-e 16x slot, so in SLI mode that has to be split between the two 16x slots for each to have 8 lanes.

[Johnmcl7]

I think all slots should be physical 16x slots. That way, whether you need a 1x, 2x, 4x, 8x, or 16x bus, all cards will fit in all slots.

It's the reason I want a DFI NF4 Ultra-D. That second 16x long slot will be perfect for an 8x long RAID controller.

Man, I wish they would make a 4x RAID controller, but I know it probably won't happen.

All you need is a bus controller that can dynamically allocate the lanes to whichever physical slot needs them.

Once they dump the old PCI slots, that would be a good idea (having all slots the large type), at the moment the problem seems to be the size of the board, the PCI-E 1x slots are so small they can cram them in near the processor/NB on the other side of the graphics card.

John