Personally I think that the best option is to save yourself a lot of hassle and buy an SLI motherboard i.e. Gigabyte Z390-GAMING-SLI.

The fact that you need a modified driver will lock you to the latest available version of the modified driver (currently 430.86) and if you need a newer driver for a newly released game you have to hope and prey that someone will patch it.

You also have to run Windows in test mode which is not very secure.

You can't bifurcate the CPU PCIe x16 slot as there is no other PCIe slot coming from the CPU on that board - you can't "give" lanes to the PCH - it is physically x4 lanes on the PCB.

To be certified for SLI on mainstream (i.e. Z series) Intel motherboards requires at least one PCIe lane switch (such as the PLX PEX8747) [Edit] so that there is suitable bandwidth available for each card when it needs it.

HEDT Intel boards (i.e. X series) don't need the PLX chip as they have more PCIe lanes natively and the ones that do have the PLX chip can run 4-way SLI/crossfire.

The board manual does label it as PCIEX4, but in the BIOS there is an option to set it to x8/x8, and when I connect the two video cards, they show as 8x speed in GPU-Z... What does this mean then?

EDIT: Check https://download.gigabyte.com/FileList/M...-elite_v3_e.pdf page 34

PCIE Bifurcation Support
Allows you to determine how the the bandwidth of the PCIEX16 slot is divided. Options: PCIE x16, PCIE
x8/x8, PCIE x8/x4/x4. (Default: PCIE x16)

EDIT2: Page 6 says

Expansion Slots Š 1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed,
be sure to install it in the PCIEX16 slot.
Š 1 x PCI Express x16 slot, running at x4 (PCIEX4)

@chinobino I won't buy a new motherboard, I am just checking I bought some used cards to resell but I was testing if I could keep one of them from mine, but I am happy with my current setup and I am waiting for the 3xxx nVIDIA cards, but if this could be possible, who knows

I was wrong about the DMI link - I just looked at a block diagram of a Z390 chipset.




If both of your x16 PCIe slots are coming from the CPU then you may well be able to bifurcate them to x8/x8 as you said.

[Edit] I have a Gigabyte Z390 UD which has three x16 PCIe slots, the top is true x16 and the bottom two are x4 electrically.

I don't have that motherboard running at the moment but I remember changing the birfurcation to x8/x8 and all that happened was the top slot halved to x8 (as the other two PCIe slots come off the PCH).

I would love to see a block diagram for your motherboard.

@chinobino How do I get a block diagram of my motherboard?

EDIT: The only way to test it I think is modding the BIOS (with someone that knows how) and testing it... I have the 2 cards and the SLI bridges... I even can place the main single GPU on the 2nd X16 slot with x8/x8 and test, although I don't know how to test PCIe bandwidth

Zitat von dsanke im Beitrag #13

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@ket From my test, the certification only check PCH.
@Lost_N_BIOS I don't know whether the PCIE from PCH support SLI or not , but I see all SLI compatible motherboard using PCIE from CPU , not PCH.

I extract SLI certification from Z390 Master and insert it to DSDT , here is the download link. http://s000.tinyupload.com/?file_id=61171507311843628073
I do not expect it work unless you bifurcate the main PCIE x16 to double x8.

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@ket Driver will check certification in DSDT and PCH , when they matching , the SLI option showing.
And I have tried flash Z370's BIOS to Z270 ,without replacing the certification in DSDT , SLI won't work, but replace SLI certification , SLI work.

Anyone know where a windows version of the tool shown in this thread is, or any windows DSDT editor? - [GUIDE] How to make your Mainboard SLI compatible without a BIOS mod
DSDTEditor-Linux-Mac-Win does not open any tool like the guide seems to imply, at least not the package I found here - https://www.techinferno.com/index.php?/f...igpu-dgpu-egpu/
First link above, in guide, the software seems to be this same tool as shown here, but I can't download it there (some error, try again later) - https://imac.hk/dsdt-editor-for-windows-...dsdt-tools.html

@DarkPoe @chinobino @dsanke

* Edit, got it working in XP, but can't get it to properly open the extracted body of DSDT GUID for SLI board BIOS so I can start looking around. It opens, but will not populate tree, so all waste of my time it looks like.
So, I don't think I can help here

I used RWEverything to get the DSDT table I posted before, but I didn't get to get the tool working to edit it and I don't know even how to edit it or what to do with it... :(

@DarkPoe - To do it that way, I'd need same table from SLI board. I don't see your DSDT table from RWE, what post #?

I just noticed, dsanke posted a mod BIOS for you at post #13, did you test it? Thank you dsanke!!
You will need to use driver chinobino linked at post #14 after you flash in the BIOS

@lost_n_bios I thought I uploaded the file though... Sorry about that

And no, I haven't tried the BIOS, can I modify it with UBU to update everything to the latest and still keep the SLI cert?

@DarkPoe - Thanks for that exported table, it's nearly exact same was what I extracted from the stock BIOS too, so being so similar it also does not open properly in the DSDTEditor
"Pairs of Brackets do not match - Tree Not Updated" is the error I get with either direct body extract or your RWE dump

Test the BIOS as it is, before you do anything with UBU - This way you know the BIOS is OK and generally bootable, before you do anything to it. I would also test the SLI stuff before further edits as well, since that is your concern here.
Never mind, DO NOT Test yet, that BIOS looks BAD! And it's a BIOS region only, so you should not flash it until properly rebuilt into a normal BIOS image.

@dsanke - what happened there?? TONS of errors in UEFITool parser vs stock BIOS? Are you sure that should maybe be bootable???
I would expect not, seeing all that, but maybe it's OK if you expect to see all those errors different than stock? Also is broken when looking at with AMIBCP, so this is definitely bad BIOS (Aside from being BIOS region only, and volumes are all moved around etc)
What happened, what did you edit it with? Why does it look so unexpectedly different and error filled? Main DXE volume is trashed too, so I can't even expand it.
The GUID with DSDT table is missing from this search now too, due to the volume being unable to decompress properly - C118F50D-391D-45F4-B3D3-11BC931AA56D - I thought maybe to extract your edit there and put into proper BIOS file, but it's missing so can't even do that
Can you please send me the edited DSDT body only, thanks

@Lost_N_BIOS It may massed up with HEX editor. Link was updated.

@dsanke - Thank you, that one looks much better Don't worry, I know more than anyone, mistakes can happen when we least expect them

@DarkPoe - New BIOS at post #13 looks OK, please test as is and check for SLI functionality before you further edit.
Flash with Qflash, Clear CMOS after, then enter BIOS and load optimized and save/reboot back to BIOS to make other changes you need, then boot to windows and check it out.

Zitat von Lost_N_BIOS im Beitrag #28

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@dsanke - Thank you, that one looks much better Don't worry, I know more than anyone, mistakes can happen when we least expect them

@DarkPoe - New BIOS at post #13 looks OK, please test as is and check for SLI functionality before you further edit.
Flash with Qflash, Clear CMOS after, then enter BIOS and load optimized and save/reboot back to BIOS to make other changes you need, then boot to windows and check it out.

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@DarkPoe - Awesome to hear it, thanks to @dsanke and @chinobino !!!
Remember, I said you need to use those modified drivers chinobino linked at post #14 - Maybe less hassles that way, or not sure, maybe similar/same stuff you did too

What made it possible is the SLI certified BIOS dsanke made you