PCI-E x16 splitter

[johnomaz]

I've seen Linus use them in builds in the past but I can't find them because I don't remember their titles.  Its a PCI-E x16 riser card that turns it into two x8 slots.  Can someone point me in the right direction.  I'm running a Gigabyte server board with a Xeon 12xx V3 series chip and 32gigs of ECC DDR4.  I will be connecting a 4 port gigabit nic card and an NVidia GTX 1050ti.  The video card is for Plex decoding so it doesn't need that much bandwidth as if it was for gaming.  Decoding isn't that frequent either but I have the card laying around and CPU decoding gets things heating up.  HEAT BAD  rawwwrrrrrrr. 

[mariushm]

use a pci-e x1 slot and riser cable for the video card. x1 bandwidth is enough for decoding.

 

those pci-e x16 "splitters" need bios and mb support, don't work with everything.

 

[johnomaz]

ya, I'm fine with using only pcie x4 bandwidth but I only have two full size pcie x16 size slots.  one being x16 and the other x8.  If I am unable to do what I need, I may have to end up upgrading which is something I don't mind but the wife will.   I'll see if I can find anything that can take one x8 and made it two x4 or the x16 and make four x4 or two x8.  I think I'm up a creek though.

[mariushm]

So wait... I don't get it, what's the actual problem?

You say you have two pci-e x16 slots... you use one for the video card and the other for the network card... job done.

 

The 4 port gigabit network card can work even on a single pci-e lane... 1 gigabit = 125 MB/s ... 4 ports is 600 MB/s ... a single pci-e 3.0 lane can do 970 MB/s ... even with a pci-e 2.0 lane that's capped at 500 MB/s the 4 port gigabit card will work just fine because you won't saturate all four ports at same time.

 

You can insert a x1 or x4 or x8 card into a x16 slot, so if the slots are close together and the video card blocks the second slot you can buy a pci-e x1 riser or a ribbon cable style extension for the pci-e slot... one of these would work : this or this

 

 

 

 

[TechMeThatsSexy]

I have been thinking about the same things. What if you dont have enough PCI slots on the motherbord and would like to use a x8 or 16 slot and split it into two x4 or 8 slots to be able to connect more PCI cards?

[mariushm]

I assume you mean pci-e, not conventional pci

 

It's SOMETIMES possible to split a pci-e x16 into 2 pci-e x8 , or 4 pci-e x4

This feature is called bifurcation and for this to work, there has to be BIOS support and possibly also chipset support.

 

Those adapter cards onto which you can install 4 m.2 ssds take advantage of this feature, splitting a x16 into 4 x4

[TechMeThatsSexy]

11 minutes ago, mariushm said:

pci-e

Yes, I was lazy and diddnt write the -e:p

12 minutes ago, mariushm said:

bifurcation

Ive looked into this. So if the motherboard supports its, what hardware do you need to split the slot? Ive been searching for someting like this:
https://www.aliexpress.com/item/4000273155502.html?spm=a2g0s.8937460.0.0.46cd2e0eJpDyKq
https://www.aliexpress.com/item/32866725427.html?spm=a2g0s.8937460.0.0.46cd2e0eJpDyKq

 

15 minutes ago, mariushm said:

4 m.2 ssds

Im interested in using 4 M.2s in RAID 0 with example "Asus Hyper M.2 X16" on one of the PCIe slots on the next motherboard I will buy.

 

 

[mariushm]

8 minutes ago, TechMeThatsSexy said:

 Ive been searching for someting like this:

https://www.aliexpress.com/item/4000273155502.html?spm=a2g0s.8937460.0.0.46cd2e0eJpDyKq
https://www.aliexpress.com/item/32866725427.html?spm=a2g0s.8937460.0.0.46cd2e0eJpDyKq

 

These don't use bifurcation.

The adapter board has that Pericom chip on it, which takes 1 pci-e lane and creates 2 or more pci-e lanes. So those 2 white pci-e slots are x16 physically but electronically they're both pci-e x1, which means a maximum of around 970 MB/s for each slot.

The chip takes data packets from each slot and mixes them on the cable sending them to the pci-e x1 slot on the motherboard, and because of this there's some extra overhead, so in reality you're probably not gonna get more than around 950 MB/s in total.

 

It's like a network switch with 5 or 8 ports ... you can connect 4 or more computers to the switch but in total all computers share the bandwidth of the outgoing network cable.

 

Cards like that hyper rely on support from motherboard and bios to split the x8 or x16 into 2 or 4 x4 channels.

 

Here's a guy selling pci-e risers that split into 2 x8 or 4 x4  or 1x8 + 2 x4 ... yeah they're expensive: https://peine-braun.net/shop/index.php?route=product/category&path=65

He also sells the boards on ebay ... here's example : https://www.ebay.com/itm/PCIe-Bifurcation-PCI-Express-bifurcated-Riser-x4x4x4x4-ITX-to-ATX/133373565840?hash=item1f0daf1b90:g:VCwAAOSw3adegGW8

 

[TechMeThatsSexy]

16 minutes ago, mariushm said:

These don't use bifurcation

I though so.. These are the only once ive seen that match the solution I see in my head. Maybe another solution?
Nice, a bit expensive...but those risers looks like what I was searching for. Thanks!