PCIe splitting for GPU mining

[madLyfe]

hey guys. im new to this type of thing so bare with me. i didnt even know this was called bifurcation. anyways here is my story.

i purchased the asrock QC5000M thinking i could use these on each of the PCIe ports(it has 3):

i would then use powered risers(pic below) from these 1x to dual adapters.

the plan was to have two cards per adapter for a total of 6 GPUs spread across the 3 PCIe slots. i was eamiling with the tech support guy after i purchased the board and he said it doesnt support it. are there any mATX that support this kind of use?

 

[jeshikat]

I take it you're mining? You'd probably have better luck asking in a cryptocurrency specific forum or subreddit.

The type of bifurcation normally discussed around here is to split x16 to x8/x8 which usually isn't what miners want since even x1 is usually good enough for that. ASRock even makes motherboards specifically for mining with lots of x1 slots though I think they're all ATX.

Like the H81 Pro BTC which according to the specs...

 

[madLyfe]

I take it you're mining? You'd probably have better luck asking in a cryptocurrency specific forum or subreddit.

The type of bifurcation normally discussed around here is to split x16 to x8/x8 which usually isn't what miners want since even x1 is usually good enough for that. ASRock even makes motherboards specifically for mining with lots of x1 slots though I think they're all ATX.

Like the H81 Pro BTC which according to the specs...

you are correct that with mining that 1x is good enough. the reason why i was looking into mATX is the size, cost, and power. all of the boards that are typically used are hard to find or have crazy markups if you do find them. im just looking to know if what im wanting is possible currently?

 

[jeshikat]

the reason why i was looking into mATX is the size, cost, and power

Size is a difference, maybe cost, but power won't be much different. Having extra slots doesn't really cost anything for power if they're not used. If there is any difference it will be completely negligible compared to the GPUs running at full load.

im just looking to know if what im wanting is possible currently?

The splitter in the first picture you posted must have some kind of PLX chip since the other end is only x1, so it should work in theory on that motherboard.

Unless someone has experience with that particular combo the only way to know is to try.

 

[madLyfe]

Size is a difference, maybe cost, but power won't be much different. Having extra slots doesn't really cost anything for power if they're not used. If there is any difference it will be completely negligible compared to the GPUs running at full load.

ya the power wont be much different, but the onboard APU probably doesnt draw much.

The splitter in the first picture you posted must have some kind of PLX chip since the other end is only x1, so it should work in theory on that motherboard.

Unless someone has experience with that particular combo the only way to know is to try.

ive been reading around and am confused with all these ppl saying that the only bifurcation cards that work are the ones by C_Payne and Ameri-rack because those have the Clock Buffer chip(also bios compatibility/software compatibility). im guessing this is for those who want to use the cards for gaming and push the cards to max lanes?

if that is what you are suggesting, i only need x1 per card, this would mean i dont need the bios compatibility or the clock buffer chip? the software wouldnt matter either because im obv not doing crossfire/SLI?

the board(QC5000M) only has 6 lanes total from what i gather:

1 x PCI Express 2.0 x16 Slot (PCIE2: x4 mode)
2 x PCI Express 2.0 x1 Slot

PCIE1 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE2 (PCIe 2.0 x16 slot) is used for PCI Express x4 lane width graphics cards.
PCIE3 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.

http://www.cpu-world.com/CPUs/Jaguar/AMD-A4-Series A4-5000.html

ive done some research on this but its new territory for me and i want to thank you for your help. i have to wait to physically test this to when i get the adapters in.

if this does work but this board just doesnt have enough lanes or something i dont mind getting a different mATX board/cpu combo to make that work but still confused as to the pci splitting to 2 or more PCI ports and using GPUs for my purpose on them. i mean they even have 1 to 3 and 1 to 4 PCI adapters:

 

[jeshikat]

ive been reading around and am confused with all these ppl saying that the only bifurcation cards that work are the ones by C_Payne and Ameri-rack because those have the Clock Buffer chip(also bios compatibility/software compatibility). im guessing this is for those who want to use the cards for gaming and push the cards to max lanes?

Right, the bifurcation discussed around here is trickier since performance and bandwidth is a concern. For GPU mining it's different since bandwidth isn't really a problem.

@EdZ knows much more about this but any of those mining adapters that connects multiple cards to a single x1 slot must be using PLX or similar because obviously you can't split x1 into x1 + x1 + x1 +x1 or whatever. If I understand correctly, the PLX chip acts much like an ethernet switch and can combine multiple PCIe devices through a fewer number of lanes.

As far as the motherboard is concerned there's only one device connected to it so you shouldn't have to worry about whether the motherboard supports bifurcation or not, the PLX chip handles it for you.

 

[EdZ]

IIRC:
If the motherboard supports bifurcation, you need a riser with a Clock Buffer chip. AFAIK nobody has tired 'chaining' risers to split from x8 to x4/x4 etc, but whether that is possible is likely dependant on the motherboard's BIOS. You can only get as many PCIe lanes as are originally available though (e.g. from a x16 slot you can only get 16 x1 lanes).
Risers with a PLX chip should work regardless of motherboard support, and as you are not gaming compatibility problems are less likely. You can also cram as many lanes as you want onto a single physical lane. PLX chips are expensive though, so these risers will cost more.

 

[madLyfe]

IIRC:
If the motherboard supports bifurcation, you need a riser with a Clock Buffer chip. AFAIK nobody has tired 'chaining' risers to split from x8 to x4/x4 etc, but whether that is possible is likely dependant on the motherboard's BIOS. You can only get as many PCIe lanes as are originally available though (e.g. from a x16 slot you can only get 16 x1 lanes).
Risers with a PLX chip should work regardless of motherboard support, and as you are not gaming compatibility problems are less likely. You can also cram as many lanes as you want onto a single physical lane. PLX chips are expensive though, so these risers will cost more.

im not sure how i would know if its got a PLX chip or not and as for the expense, these are only like $20 or so each. not sure if that is expensive or not?

you can see the PCI 1 to 2 adapters as well as varied versions of straight risers that everyone uses with no problems in this listings list.

http://www.ebay.com/itm/30226871337...49&var=601111124393&ssPageName=STRK:MEBIDX:IT

lets just say there is no issue with using a PCI 1 to 2 or 1 to 3 or 1 to 4 adapters, everything worked perfectly, how many GPUs could be handled with the PCI specs on that board with the chipset/controller?

 

[jeshikat]

That's far too cheap for genuine PLX chip. So I'm not sure if it's some cheaper alternative or if they're using some other method entirely.

Assuming the 1:4 adapter works, then you should only be limited by how many slots there are on the motherboard.

 

[madLyfe]

Assuming the 1:4 adapter works, then you should only be limited by how many slots there are on the motherboard.

sorry to be nitpicky, but when you say limited by the number of slots on the board, you mean by whatever ratio adapter I use(1:2, 1:3, 1:4) per slot or that the board only had 3 slots so I can only use 3 GPUs no matter the adapter?

 

[iFreilicht]

sorry to be nitpicky, but when you say limited by the number of slots on the board, you mean by whatever ratio adapter I use(1:2, 1:3, 1:4) per slot or that the board only had 3 slots so I can only use 3 GPUs no matter the adapter?

He meant the former.

 

[aquelito]

An other case study with an active riser this time : potentially any mini-itx board is compatible.

https://forum.level1techs.com/t/the...of-an-old-pc-into-a-god-like-system/104756/19

 

[EdZ]

http://www.ebay.com/itm/30226871337...49&var=601111124393&ssPageName=STRK:MEBIDX:IT

That does not split a 1x PCIe port to two PCIe ports, it uses a PI7C9X111SLBFDE bridge chip to turn an x1 PCIe port to two PCI ports (technically, to one PCI bus with two ports on it, PCI uses a single shared bus for all ports).

In theory, if you didn't care about bandwidth in the slightest, you could use these birdge chips to turn individual x1 PCIe lanes into a set of PCI buses, then the same chips (they are bidirectional) to put multiple PCIe cards onto each of those busses. You'd have all cards on that bus share the same 133MB/s bandwidth, and you'd probably run into signal issues due to not being able to pack the cards physically close enough together, but that would be a cheap way to cram as many GPUs as possible onto a system. Certainly not an existing solution, so you'd need to create a custom board to do so, and an ugly, ugly hack to boot.

 

[madLyfe]

You'd have all cards on that bus share the same 133MB/s bandwidth, and you'd probably run into signal issues due to not being able to pack the cards physically close enough together, but that would be a cheap way to cram as many GPUs as possible onto a system. Certainly not an existing solution, so you'd need to create a custom board to do so, and an ugly, ugly hack to boot.

mining rigs are not for looks by any means but they have their own beauty:

im still not sure i fully understand the signal part but i think i get that it turns a x1 PCIe port into a PCI bus with two ports. what about with a PCIe x16 port?

so w/o physically making a custom board there is no way to get 6-8 cards spread across the 3 PCIe ports

PCIE1 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.
PCIE2 (PCIe 2.0 x16 slot) is used for PCI Express x4 lane width graphics cards.
PCIE3 (PCIe 2.0 x1 slot) is used for PCI Express x1 lane width cards.

on the board i posted above(QC5000M)?

 

[EdZ]

on the board i posted above(QC5000M)?

On that board? Because it does not support PCIe Bifurcation, your only options are expensive PLX splitters or an (also expensive) custom solution. In either case, it would just be cheaper to simply buy a motherboard with the correct number of slots to start with.

 

[madLyfe]

On that board? Because it does not support PCIe Bifurcation, your only options are expensive PLX splitters or an (also expensive) custom solution. In either case, it would just be cheaper to simply buy a motherboard with the correct number of slots to start with.

and this is because the 1:2-4 adapters dont turn the expanded ports into PCIe ports but into PCI ports and the the cards wont run on those?

i was reading here Would this work? 2 cards per PCI slot?! that this is working, though with limited information. the commentor rufus_francis is the one who claims it works in the 3rd comment:

I've tested this and it does in fact work. Some older mobos don't like it and give them both half bandwidth. Otherwise its OK. Also I've followed you on Instagram for like a year and I really like your page. You should post something about your mining rig on there!

so i dunno what to think...

 

[jØrd]

fwiw people have been doing this for years. if you want to pay out the ass for it the data centre vendors have you covered
http://cyclone.com/products/expansion_backplanes/index.php
http://cyclone.com/products/expansion_systems/index.php

Essentially bifurcation requires support from the motherboard and enables one slot to be used w/ two cards using the correct type of riser. Whats being discussed and linked in this thread tends to be referred to (in my anecdotal experience) as an expander and does not require a motherboard w/ support baked in.

 

[madLyfe]

Essentially bifurcation requires support from the motherboard and enables one slot to be used w/ two cards using the correct type of riser. Whats being discussed and linked in this thread tends to be referred to (in my anecdotal experience) as an expander and does not require a motherboard w/ support baked in.

so this should work on most boards? if that is the case is there a limit to how many cards that specific board can handle?

 

[jØrd]

is there a limit to how many cards that specific board can handle?

how many cards are you expecting to be running? Cyclone make some pretty huge expanders.

 

[madLyfe]

how many cards are you expecting to be running? Cyclone make some pretty huge expanders.

6-8? Windows maxes out at some point. plus using the adapters I linked to. cost is the biggest issue. large and expensive adapters don't fit that model.