Can you split pcie lanes for one device (for example pcie 2.0 x1 to pcie 1.0 x2)

[Transpanda]

I don’t have high hopes for this, but I’ll ask anyways, mostly out of curiosity.

Is it possible to use a pcie 2.0 x1 slot on a motherboard and use an active adapter to split the lanes. Resulting in double the lanes at half the speed or one pcie generation older. My thought process is that the chipset and gpu mining splitters do something similar. The difference is they share a set amount of lanes between multiple devices and I’m wondering if I can split lanes for one device.

In case you’re wondering why: I have a pcie 1.1 x4 card and want to use it in a pcie 2.0 x1 slot. So converting the pcie 2.0 x1 slot into a pcie 1.0 x2 slot would be beneficial.


Thank you for your input :3

 

[Ruru]

I don't see any idea in your example since aren't 1.0 x2 and 2.0 x1 the same what it comes to bandwith? Or do I just need more coffee to understand what you're meaning

 

[Assimilator]

Not without a dedicated chip specifically designed to split and combine lanes, and those are dead in the consumer space. PLX Technology were the guys doing this about a decade ago but then they got bought by Broadcom, reoriented to server, their products became stupidly expensive, and that was that for consumers.

Nowadays server hardware offers so many PCIe lanes that there's almost no need for such chips, thus they are extremely niche and therefore expensive. Take the EPYC SIENA that has 96 PCIe 5.0 lanes, of which 32 can be dedicated to SATA3 ports - even though SATA3 bandwidth is only 15% of a PCIe 5.0 lane's, it's fine to waste that unused bandwidth because doing so is cheaper than using a chip like the type that I mentioned.

 

[arbiter]

I don't see any idea in your example since aren't 1.0 x2 and 2.0 x1 the same what it comes to bandwith? Or do I just need more coffee to understand what you're meaning

I would say transpanda is looking for a PCI riser card like crypto miners use to plug x16 cards in to x1 slots. If any of those cards has its own PCIe chip on it to do what is wanted not sure if there are any.

Are you a human?

www.newegg.com

 

[Ruru]

PLX Technology were the guys doing this about a decade ago

Like with dual-GPU graphics cards?

 

[Onasi]

@Ruru
I seem to remember that the PLX chips on, say, 690 or 7990 weren’t affecting the PCI-e bandwidth or lanes at all and were just for the two GPU chips to be able to communicate with each other. I might be wrong on that, but I don’t THINK I am?

 

[Ruru]

@Ruru
I seem to remember that the PLX chips on, say, 690 or 7990 weren’t affecting the PCI-e bandwidth or lanes at all and were just for the two GPU chips to be able to communicate with each other. I might be wrong on that, but I don’t THINK I am?

IIRC they split the incoming x16 to two x8 for the two GPUs. I may be wrong and I don't know THAT much about those things.

 

[Onasi]

@Ruru
Don’t think it was a split exactly. Currently looking at the GTX 690 and the PEX 8747 provided 48 lanes of Gen 3 - 16 to each GPU and the remaining 16 to the slot. Stupidly complex thing.

 

[Assimilator]

Like with dual-GPU graphics cards?

Yes, they used PLX chips too!

 

[Ruru]

@Ruru
Don’t think it was a split exactly. Currently looking at the GTX 690 and the PEX 8747 provided 48 lanes of Gen 3 - 16 to each GPU and the remaining 16 to the slot. Stupidly complex thing.

Interesting. I guess that all the consumer dual GPU cards had a similar solution.

 

[Onasi]

Yes, they used PLX chips too!

NV actually had their own NF200 before moving to Gen 3 and switching to PLX chips IIRC.

 

[Ruru]

NV actually had their own NF200 before moving to Gen 3 and switching to PLX chips IIRC.

That was also implemented on some motherboards, like nF680/780 didn't generate heat enough...

 

[Transpanda]

I don't see any idea in your example since aren't 1.0 x2 and 2.0 x1 the same what it comes to bandwith? Or do I just need more coffee to understand what you're meaning

I’ll use another example to explain what I mean: Let’s say you have a gpu that has 16 lanes of pcie 3.0, but your motherboard and cpu combo only supports 8 lanes, which however are pcie 4.0. The theoretical speed is the same, but the old card doesn’t support pcie 4.0, so its limited to half the speed (pcie 3.0 x8). If you could split the 8 pcie 4.0 lanes into 16 (1x4.0 lane to 2x3.0 lanes), you’d have 16 lanes of pcie 3.0, allowing the gpu to use the full bandwidt.

I’m trying to do that but with a pcie 2.0 x1 slot splitting it into pcie1.0 x2

Hope this is easier to understand.

 

[Transpanda]

I would say transpanda is looking for a PCI riser card like crypto miners use to plug x16 cards in to x1 slots. If any of those cards has its own PCIe chip on it to do what is wanted not sure if there are any.

Are you a human?

www.newegg.com

In a way, I’m not totally sure what kind of pcie chip you’re referring to, so we might be thinking of the same thing. But that formfactor would probably work best. Most mining risers support pcie 3.0 x1. If the mentioned pcie chip could split that into pcie 2.0 x2 / pcie 1.0 x4, then yes. that would work for what I’m trying to achieve.

 

[TheLostSwede]

Not without a dedicated chip specifically designed to split and combine lanes, and those are dead in the consumer space.

Actually, you'd be mistaken there, as ASMedia has a range of PCIe bridge chips these days, but so far, they're limited to PCIe 3.0 as their fasted product offering.
They also don't have one suitable for going from 1x x16 to 2x x16, which is what I guess is what PLX was widely known for. These are more used in products that need a few more PCIe lanes.

PCIe Bridge|ASMedia Technology Inc.

ASMedia Technology was founded in 2004 and went public in 2012 (stock code: 5269.TW). Headquarter is located in Taiwan. ASMedia specializes in high-speed interface technologies with strong expertise in high-speed SERDES in house development. Company strives for continual innovation and the...

www.asmedia.com.tw

Microchip also has a range of them, but as you say, not for consumer applications, as they're expensive.

 

[Assimilator]

Actually, you'd be mistaken there, as ASMedia has a range of PCIe bridge chips these days, but so far, they're limited to PCIe 3.0 as their fasted product offering.

PCIe Bridge|ASMedia Technology Inc.

ASMedia Technology was founded in 2004 and went public in 2012 (stock code: 5269.TW). Headquarter is located in Taiwan. ASMedia specializes in high-speed interface technologies with strong expertise in high-speed SERDES in house development. Company strives for continual innovation and the...

www.asmedia.com.tw

Thanks, I honestly wasn't aware ASM made such chips; a PCIe 4.0 (not even 5.0) version of their 2824 (x8 to x24) would make a killing in the consumer market, if priced right. Imagine X570 with one of those chips in PCIe 4.0, would satisfy all my needs

 

[Ruru]

I’ll use another example to explain what I mean: Let’s say you have a gpu that has 16 lanes of pcie 3.0, but your motherboard and cpu combo only supports 8 lanes, which however are pcie 4.0. The theoretical speed is the same, but the old card doesn’t support pcie 4.0, so its limited to half the speed (pcie 3.0 x8). If you could split the 8 pcie 4.0 lanes into 16 (1x4.0 lane to 2x3.0 lanes), you’d have 16 lanes of pcie 3.0, allowing the gpu to use the full bandwidt.

I’m trying to do that but with a pcie 2.0 x1 slot splitting it into pcie1.0 x2

Hope this is easier to understand.

Ah, like on my case, where my CPU supports PCIe 4.0 but I have only a PCIe 3.0 board?

 

[Wirko]

Here's a card with a Pericom PI7C9X bridge chip, working at PCIe 2.0 speeds, and it seems to be just what the OP needs:

https://www.aliexpress.com/item/32868079091.html

(search for "pcie switch card" or "pcie bridge card" on Aliexpress or Ebay, there might be other options at an acceptable price)

 

[Assimilator]

Here's a card with a Pericom PI7C9X bridge chip, working at PCIe 2.0 speeds, and it seems to be just what the OP needs:

https://www.aliexpress.com/item/32868079091.html

(search for "pcie switch card" or "pcie bridge card" on Aliexpress or Ebay, there might be other options at an acceptable price)

That's muxing/demuxing a single 2.0 x1 link to qud 2.0 x1 links i.e. losing bandwidth, OP wants to get a 1.1 x2 link from a 2.0 x1 link i.e. retaining bandwidth - not the same at all.

 

[TheLostSwede]

Thanks, I honestly wasn't aware ASM made such chips; a PCIe 4.0 (not even 5.0) version of their 2824 (x8 to x24) would make a killing in the consumer market, if priced right. Imagine X570 with one of those chips in PCIe 4.0, would satisfy all my needs

I didn't expect you to be either, as it's not as if it's something that has been widely covered by media in general and almost no desktop motherboards appears to be using them. I think I've seen one that used a basic 1 to 3 switch or something along those lines.

 

[Frick]

Thanks, I honestly wasn't aware ASM made such chips; a PCIe 4.0 (not even 5.0) version of their 2824 (x8 to x24) would make a killing in the consumer market, if priced right. Imagine X570 with one of those chips in PCIe 4.0, would satisfy all my needs

I don't think they would make a killing, because most people who buy consumer motherboards don't add cards beyond GPU and so why include them? The ship has sailed, the horses have left the barn, etc. There would be a market for it sure, but not "make a killing" market.

 

[bug]

I’ll use another example to explain what I mean: Let’s say you have a gpu that has 16 lanes of pcie 3.0, but your motherboard and cpu combo only supports 8 lanes, which however are pcie 4.0. The theoretical speed is the same, but the old card doesn’t support pcie 4.0, so its limited to half the speed (pcie 3.0 x8). If you could split the 8 pcie 4.0 lanes into 16 (1x4.0 lane to 2x3.0 lanes), you’d have 16 lanes of pcie 3.0, allowing the gpu to use the full bandwidt.

I’m trying to do that but with a pcie 2.0 x1 slot splitting it into pcie1.0 x2

Hope this is easier to understand.

There's PCIe bifurcation. But it doesn't do what you need. And I'm not even sure is was there before PCIe 3.0 or so.

 

[Ware]

I have a pcie 1.1 x4 card and want to use it in a pcie 2.0 x1 slot

 

[Wirko]

That's muxing/demuxing a single 2.0 x1 link to qud 2.0 x1 links i.e. losing bandwidth, OP wants to get a 1.1 x2 link from a 2.0 x1 link i.e. retaining bandwidth - not the same at all.

True. It's all x1, I missed that. I also see that Pericom makes a bunch of different PCIe switch chips, up to Gen 3 - their range is similar to that of Asmedia.

The Marvell 88NR2241, which used to be consumer-friendly (the once-popular WD AN1500 card runs on it) still exists too but isn't consumer-friendly anymore.

@Ware In addition to Dremel the cutter, you also need the Lemerd tool, which magically adds lanes where there are too few.

 

[Apocalypsee]

If your motherboard is mATX and you use ATX case you can always use riser cards like this

I use x1 to x1 riser to relocate my soundcard further bottom the case so it won't suffocate the GPU