A few PCI questions.

I've searched around and not been able to find clear answers to these. Any help is gratefully received!

Most motherboards with two PCIEx16 slots work that if you only fill the first, it functions at x16 and if you fill the second as well, they both run at x8. I understand that but if I put a GPU in one and something like a PCI-E SSD in the other, which would only need x4, will the first one still halve?

It's probably helpful if I explain what's behind these questions. I have an insatiable need for hard drives. At least four large traditional drives on SATA (I have four WD Caviar Black) and then at least two regular SSD which I already have, and then I would like to add a PCI-E SSD as fast as possible and then a second one later on. I have a graphics card (R9 285 which will probably be upgraded one day but not any time soon). So all together I'm looking to put in one GPU, two four-lane PCI-E SSDs (either into a PCI-E slot or via M2), two regular SSDs on SATA and four HDs on SATA.

I highly doubt my little r9-285 would suffer from being at x8, so I don't care about that (unless I'm very wrong?), but I need to make sure I can get the rest in on whichever motherboard I buy. I'm thinking from the above that I need 24 PCI-E lanes and that an i7-5820K would therefore be sufficient? The SATA ports don't count towards this total, right?

Thanks for any help. Motherboard recommendations are also welcome. Though I am wary of MSI historically.

Oh dear. 89 views and not one reply. Was my question too vague or just nobody knows?

h4rm0ny said:

I've searched around and not been able to find clear answers to these. Any help is gratefully received!

Most motherboards with two PCIEx16 slots work that if you only fill the first, it functions at x16 and if you fill the second as well, they both run at x8. I understand that but if I put a GPU in one and something like a PCI-E SSD in the other, which would only need x4, will the first one still halve?

Click to expand...

SATA don't count towards the total, they aren't using pcie lanes.

For sharing the bandwidth, it depends on the board. You'd have to look up invidiual boards to see how the lanes are shared on that board.

Example, my board (GA-x99-sli) only PCIE_1 is x16 with a 5820k installed. PCIE_2 (the other x16 slot) is only up to x8. But you can plug stuff into it without capping the bandwidth of PCIE_1. PCIE_4 shares with 1, so anything in there, caps 1 to 8.

On the above board (it's been replaced with the x99p-SLI), you could do exactly what you want by putting the card in PCIE_1, one SDD in PCIE_2 and one in PCIE 4 and and nothing would be capped. Card would run at x16, both ssd at x4.

Running at times x8 wouldn't bottleneck the card anyway, almost no difference between x8 and x16.

So yeah, you should easily be able to run two ssd and a x16 gpu on a 5820k. But you need to look in the manual/specs for whichever board you buy to see how the lanes are split, which slots effect which and so on and any other considerations (does using m2 disable a slot, which slot etc).

Armadillo said:

SATA don't count towards the total, they aren't using pcie lanes.

For sharing the bandwidth, it depends on the board. You'd have to look up invidiual boards to see how the lanes are shared on that board.

Example, my board (GA-x99-sli) only PCIE_1 is x16 with a 5820k installed. PCIE_2 (the other x16 slot) is only up to x8. But you can plug stuff into it without capping the bandwidth of PCIE_1. PCIE_4 shares with 1, so anything in there, caps 1 to 8.

On the above board (it's been replaced with the x99p-SLI), you could do exactly what you want by putting the card in PCIE_1, one SDD in PCIE_2 and one in PCIE 4 and and nothing would be capped. Card would run at x16, both ssd at x4.

Running at times x8 wouldn't bottleneck the card anyway, almost no difference between x8 and x16.

So yeah, you should easily be able to run two ssd and a x16 gpu on a 5820k. But you need to look in the manual/specs for whichever board you buy to see how the lanes are split, which slots effect which and so on and any other considerations (does using m2 disable a slot, which slot etc).

Click to expand...

Thanks for taking the time to write that. Much of it is what I thought, but I wanted to be sure before parting with the money. It's a pretty big system overhaul to get wrong because I made assumptions.

Appreciate it!

I currently have:
Intel 750 (4x pci-e)
Samsung 951 m.2(4x pci-e)
M500 SATA SSD
SK hynix SATA SSD
2TB WD Red SATA
4TB HGST SATA

My GPU still runs at 16x. If you think you might add more PCI-e SSD's latter, it could be better to get the 5930K as it has 40 lanes.