mirddes

Have been searching for this info for sometime, thanks for the post. I knew my CPU supported PCI-E Bifurcation (Skylake i7/6700) but my motherboard(Q170m) didn't.
 
@grayxu The grounding pins are quite far from the CFG 5 and 6 points for the 6700. So I assume you would need to do this on the socket instead with a tiny bit of wire?

 

My AMD Gigabyte B550 D3SH has it, and I think it's literally the cheapest MB you can buy with that chipset. But maybe that's the key, 550 vs 450, etc..

Huh? Last I checked both AMD and Intel mobos had this feature only in the expensive models. I couldn't find any cheap AMD mobo that supports it. It's a feature that depends on a hardware implementation, it's not just artificially limited.
 
 
Oh and this forum is mostly into gaming and discussing anything not related to gaming will get you blank stares. 🙃
That's actually the case for most computer forums, I'm still looking for one that isn't like that.

Incorrect:

You can't push x8 lanes through a slot that only has wires for x1 or x4.  It physically doesn't work.  
 
See the reverse on the RX-6500

It's an x16 slot on the card, but it only has wires connected for x4 to the pins.  The rest aren't even connected, so no matter what you "hack" it can't do x8.  

Here's how you avoid needing to do all of this hardware hacking:

If you're enough of a power-user to actually need the 8x8 setup, make sure you buy hardware that supports it out of the box, rather than by voiding warranties and potentially killing hardware with sketchy modifications.  
 
Because amongst other things:

Just because your board has an x16 slot doesn't mean it's wired for x16.
 
My most recent B550 purchase was stacked with 5x x16 slots.  Only 1 of which is wired for 16, the rest are x1 or x4.  Without the physical wiring, you can't make it run at 8x8.

Again, can you elaborate?
 
What exactly do you mean by "PCI-E bifurcation"? I assume you mean splitting for example one PCIe x16 port into two PCIe x8 ports.
I looked up some lower end Z77 boards and found that for example the Gigabyte GA-Z77-D3H has two full size x16 slots, but one runs at x16 speeds and the other runs at x4 speeds. It is not possible to make them both run at x8. Is that what you are saying you have gotten around by shortening some pins on the CPU?
 
I also looked up some lower end AMD motherboards such as the Gigabyte GA-AX370-Gaming 3 and the spec sheet there says the exact same thing.
One x16 slot running at x16.
One x16 slot running at x4.
 
No mention of running both at x8.
So I don't really think this is an Intel-exclusive thing that doesn't exist on AMD motherboards. 
 
 
Are you sure that it is a software lock and not a hardware limit?
I am fairly sure this is a cost-saving measurement done by motherboard manufacturers. That they only physically make traces in the motherboard for an x4 connection to the second PCIe slot.
 
Maybe I am complete off base here and you are right that motherboard manufacturers are locking this with software and you have found a way around it, but as it stands right now I kind of doubt it to be honest. 
Without looking into it too much, I wouldn't be surprised if you shortening the pins on your CPU just results in your CPU being tricked into thinking it has two x8 connections, even though the second port still only has an x4 connection. If that is the case, you might get a lot of corrupt data if you start pushing the second "x8" connection so that it tries to use all 8 lanes.

OP can you please elaborate what you are trying to say?
It seems like everyone is confused. What is the practical end result of this guide? What paywall are you talking about? How does AMD and Intel differ in this regard?

from what i can make of it, OP somehow found a Z77 board that only has a single full length slot, and is upset that the bios doesnt magically let him break up that slot into the options that the cpu could theoretically output.

This is awesome. <3's for OP. Shame half the responders have nfc wtf.
 
Was curious how possible this might be; not having easy access to proper datasheets doesn't help. My BIOS doesn't have any bifurcation options but does have a hidden CPU PCIe Lanes Configuration that I was hoping would split the CPU slot to x8x8 or something, but wasn't sure how that might work out because it seems like it's usually geared towards splitting across multiple physical slots on a board, where I only have one x16 CPU slot.
 
So, because of this thread I have some hope the option could do what I wanted and, apparently, alternately now have a secondary way to do it.
 
Neat.
 
For details: my board has a x16 CPU slot then 1*x16 (x4 electrical) 4*x1 PCH slots (MSI Z390-A PRO) and I have a GPU (2070 Super) in the main x16 slot and another GPU (3060) in the secondary x16 slot (which I originally thought/assumed was at least x8).
 
Both GPUs coolers block x1 slots where I only have one x1 actually exposed. I've found a small bendy x1 riser that I stuffed under the 3060's shroud to extend one out.
 
So then I also have a Thunderbolt card and an M.2->PCIe card, both able to use x4 but stuck at x1.
 
Thunderbolt card does work but seems to occasionally have some weirdness/issues which is possibly caused by my board expecting it to be installed in the second x16 (which is only x4) slot.
 
I don't think that running the 2070S at x8 would make a noticeable difference; I didn't even realize the 3060 was at x4 and not x8 until now anyway and didn't notice any major performance issues with it, though it is a secondary card.
 
Splitting the main CPU x16 to x8x8 would allow me to run both GPUs at x8 and free up the second "x16" (x4 electrical) for the Thunderbolt card as MSIGOD Intended. Also, since I'd need to get creative with risers and such to make it work physi-electrically, I'd free up any x1 slots covered by GPU coolers (I'd probably make or 3D print some kind of GPU chassis for them or at minimum swap to a case that allows vertical and horizontal PCIe mounting, though that only really would give a spot for one of the two GPUs)
 
This would also allow me to run the second M.2 drive in a Thunderbolt enclosure (which I could do now, but the Thunderbolt is in an x1 slot, so it'd be slower if anything), freeing up an x1 slot and allowing it potentially (depending on connected Thunderbolt devices) more bandwidth than the x1 could manage.
 
The alternative is putting the secondary GPU in one of the x1 slots and the Thunderbolt in the second "x16" (x4 electrical) slot, which is definitely easier than BIOS hacking and everything else and not entirely the worst option as I mostly only use it for extra screens but I haven't been able to bring myself to do this yet, not for much good reason though; MultiGPU in DX12 etc. is never really implemented anywhere and other than stuff like Blender or other rendering/dGPU/CUDA is the only other major use case which I think, for most things, compared to gaming, is likely light on bus bandwidth usage... but why do the easy thing when I can hack stuff instead? 😉

as strict definition? maybe. But:
 
I LOVE Paywalls. Thanks Intel! - ECC Support on Alder Lake
 

I have to say I agree with this. That's also the reason why I "hacking" an old CPU instead of those for production.
Still, I want to say that this feature is easy to enable for MB makers on any platform, but they don't. It's called a "paywall".
 
but it seems like you also don't get the definition "PCI-E Bifurcation"... This has NOTHING to do with HW cabling.

Well, I guess you just don't get the definition "PCI-E Bifurcation". 
 
exapmle 1: only one x16 PCI-E slot
before: only one PCI-E devices in this slot.
now: you can attach three devices (x8+x4+x4) in one x16 PCI-E slot
 
example 2: 2 x16 PCI-E slot (not PCH)
before: only x8+x8
now: with a x8 device in the first slot, you can install two x4 devices in the second x16 slot
 
You should check https://www.10gtek.com/new-1414.

Ah I see, I get it now. So it's just Intel being Intel as usual. Just like how they lock down overclocking to specific CPU models and I believe specific chipset as well (unless that changed, haven't kept up with Intel).

Z77 is only my case.
For 12 gen CPU, 8+8 bifurcation in single PCI-E slot is only provided on high-end Z690+DDR5. With hard strap, you can get same feature in any Z690 board.
Yeah, such scenarios are not for gamers like I mentioned in the first paragraph.
This tutorial is for those building workstation or servers on cheap MBs.

"practical end result": You can get PCI-E bifurcation feature in low-end MBs.
"paywall": PCI-E bifurcation is only available on Intel high-end MBs, however, it is enabled on almost all AMD MBs.

The Paywall of PCI-E Bifurcation

PCI-E provides CPUs the ability to connect with fast devices, like >10 Gbps networks, NVMe SSD, etc. Especially for the usage of workstations or servers, the number PCI-E slots means a lot. As a result, Xeon CPUs and server-level MBs provide more PCI-E slots than on the consumer level. On the other hand, the number of PCI-E slots on cheap MB is usually only 1 for GPU. However, those server-level MBs are more expensive.
PCI-E bifurcation is an approach to split x16 PCI-E channels into different combinations, like 8+8 or 8+4+4. Since some PCI-E devices are only in x4 or x8 speed. But unlike AMD, Intel consumer-level MBs rarely offer such an option in the BIOS, let alone the lower-end products.
Note: PLX chips can also help you like a switch, but they are also expensive.
Bypass the paywall

Let’s do some hacking to bypass such paywall. My platform is Intel Core i5-3450 + Z77, but I guess this method is also useful for any Intel CPU with public datasheet information, like 12th gen CPU[3].
First, go to the Intel ark document webpage to check the “PCI Express Configurations”, which will show all bifurcation modes that your CPU supports.
For my CPU, 16=8+8=8+4+4, which provides the opportunity to place one x8 HBA card and 2 x4 NVMe SSD in one PCI-E slot! 
 

 
Second, get the datasheet of your CPU, and search for bifurcation-related content. You will find the config (CFG) to control PCI-E bifurcation.
note: the datasheet contains infos like the definitions of LGA1155, so that we can control it manaully.
 

 
As the fig above, the value of CFG[6:5] controls bifurcation modes on my platform, and:
00: 8+4+4 10: 8+8 11: 16 note: CFG[17:0] means 18 pins of LGA1155.
And then we search the positions of CFG pins to hard-set their values as we wish.


 
It shows that CFG[5] is N35, and CFG[6] is L37. So that we can find the actual physical position of CFG[5] and CFG[6].
 

 
As mentioned above, I want to set 16=8+4+4, so the values of CFG[5] and CFG[6] should be both 0. So we can ground CFG[5] and CFG[6] by connecting N35<->M35 and L37<->M37. (VSS is GND, and VCC is PWR)
I used some silver paste to make such hard strap.
 
 
 
Last, get a cheap PCI-E bifurcation card with clock MUX, like multiple NVMe SSD in one card.


 
my config places one LSI2308 with other NVMe SSDs in one PCI-E card. 
 

 
Now you can enjoy multiple devices with fast connections!
 
 
 
Small modification, big impact. So why MB producers disable this feature?
 
FYI: I tried to use AMIBCP tools to modify potentially hidden options in BIOS firmware, but sadly found nothing
 

I might be reading this wrong, but I think this is something different from just having PCI-e slots that are capable of certain speeds.
And more like taking a single slot and making it be 8+4+4 by itself while leaving the others alone, to have 3 different devices plugged in that one slot and be recognized individually ?
Whichever the case, I don't personally have any need for this.

calling this "the paywall of bifurcation" is...  at least a bit excessive.
 
every motherboard i own is at least 8+8 capable. the reason why most consumer boards these days only do x16 is quite simple:
- the majority of people doesnt use more than one slot (for their GPU) and one or two M.2 slots, which these days dont tap into those x16 GPU lanes.
- the majority of other PCIe slot devices are 1x, which means that past the 3 slots we keep for the GPU these days, everything else can get a 1x slot from the chipset without tapping into the GPU's lanes, and still have bandwidth for an NVME SSD.
 
the market of people who want to have a desktop platform with 8x, 4x, 4x, 4x, 4x (assuming 20 cpu lanes and 4 chipset lanes) is so small there's literally douzens of us. And economy of scale tells us that if you want a board with a market of douzens of people, it will be more expensive.
 
also, where the FLIP did you find a Z77 board without crossfire support?

Basically all ram speed is measured in MTs, but often incorrectly labeled as MHz. So task manager is wrong, and it should say 1200MHz or 2400MTs.
 
Faster rated memory will work fine, and just run at the slower speed.

I have an hunanzhi mother board à x99 QD4 but I can't manage to make the bifurcation work. there is a setting for that in the bios but it doesn't seem to work. I maybe need to modify other settings but I don't know which one. 

I propose Linus Sebastian interview Linus Torvalds.

real company stuff.
same name same industry  #SameNameMeme
 
especially after dreamhack.

just wanted to quote a chinese guys youtube comment that claims to have experience with these.
"kenny so 
Dear linus, I'm KENNY, a budget gaming PC builder in HK, and im always working around with chinese MB, yours is not the most unthinkable chinese MB I've been working with, chinese MB on LGA1151 are much more then you can imagine, and actually the one you're playing with was not meant to work with high end CPU like 8700k, it's meant for budget PC with a i3 8100, g4560, G5400 with ECC REG DDR3 (yes, your board dose support) since they are as cheap as rubbish in China, the reason you can't get the full power out of your CPU is because you haven't run through your BIOS yet, all the power control value has to be manually config manually to make your cpu turbo up in the right way, if your are not tuning it right, only one of the 6 cores will turbo up to the right speed. thats how you lost your CPU performance, you can make it right in BIOS or through INTEL XTU. And about Intel lied....Actually they do, i'm sure what they've done is just changed the microcode the make your MB unable to recognize older CPUs , the truth is we've found out all 100,200,300 chipsets can support through all 4 generations of 6,7,8 and 9 with a simple bios MOD, not only chinese MB can do that, just add in the microcode of the generation of the cpu you want, even a h110 can perfectly support a 9900k, and a z390 can run a 6700k, and we've also seen some chinese geeks had a breakthrough to run a Xeon E-2186G on a Z170 motherboard. The home gaming ITX rig i'm using myself, is using a i7 9700K engineering sample with a ASUS Z170i PRO GAMING, and it worked just fine with a GTX 1080Ti and DDR4 3000 and even overclockable... because In HK 100 and 200 MB are dirt cheap, like around US$15~US$20 to get a perfect condition 2nd handed ASUS, GIGABYTE, MSI, ASROCK....etc And also because we HK buyer wont have to pay extra transport fee to get those cheap server retired ECC RAM and cheap CPUs form taobao and aliexpress, I3 8100 and i5 8400 on a h110 and b150 MB become one of my best choice besides X79 and Lga 1156 to build budget gaming PCs with. thats why i'm always messing with all those bios adding in the CPU microcode i needed, So I'm pretty sure with this~ you just search online and you can easily find packed microcode module to add into EFI bios, its just as simple as adding a NVMe support to 2~4 gen MB, And BTW, almost every DDR3 MB can do ECC REG support too, also a little mod of the BIOS will do.... "

The H310C chipset is a 22nm edition of the H310 chipset. 
All 100, 200 and 300 series motherboards can support skylake, Kabylake and Coffeelake CPUs, with modified BIOS and CPU Microcodes. There’re only minor differences in pin layouts between the LGA1151 from skylake/kabylake and the one from coffeelake, only 2 more pins are utilized for power delivery.  You can run a quad core 8th gen CPU like the i3 8100 with only the BIOS modification on a 100 or 200 series motherboard, but if you wish to use 6-or-8-core CPUs with 100/200 series motherboard, you’ll need to disable the two pins (and possibly a few other pins according to the design of your motherboard, because some brands have unused pins attached to power as well) with tapes, or else the current on those 2 pins WILL DAMAGE the board. A high quality old board is better for this purpose, because 6-and-8-core CPUs do consume more power. Because manufacturers didn’t test newer CPUs on old boards, CPU voltage might be a little higher than expected, but you can adjust it manually.