I there any AM4 or LGA1200 motherboard that is uATX and supports dual x8 mode on two x16 slots?

inf3rno

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I struggle to find any uATX board with these features. All of them supports dual x16+x4 instead of dual x8/x8. Is there any exception?
 

chithanh

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Yes, ASRock Rack X570D4U and X570D4U-2L2T.

There are also some TR4 and LGA2066 µATX mobos that support x16/x16 even.
 

inf3rno

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Yes, ASRock Rack X570D4U and X570D4U-2L2T.

There are also some TR4 and LGA2066 µATX mobos that support x16/x16 even.
Yes, I meant consumer boards. ASRock Rack is server stuff afaik, I am not even sure where one can buy it and it is way out of my budget I guess.
 

inf3rno

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For example in the case of LGA1151 there are a few Asus boards around $200 that support it. https://origin-www.asus.com/Motherboards/TUF-Z390M-PRO-GAMING/specifications/ I don't understand why almost every uATX board supports only x16+x4 or if I would go for mITX + a bifurcation riser instead, then why no company is manufacturing bifurcation riser cards for consumers when their boards support 2x8? Looks like all I want is server grade stuff. :D
 

doubletake

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-EDIT-

Disregard, that was just the bifurcation support for slot 1 that was listed; its secondary x16 slot is also only x4 off the chipset.

-EDIT2-

Seems like the Z490M Gaming Edge does actually do it. MSI at least helpfuly indicates the presence of this feature on boards by having both x16 slots steel-cased.
 
Last edited:

inf3rno

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-EDIT-

Disregard, that was just the bifurcation support for slot 1 that was listed; its secondary x16 slot is also only x4 off the chipset.

-EDIT2-

Seems like the Z490M Gaming Edge does actually do it. MSI at least helpfuly indicates the presence of this feature on boards by having both x16 slots steel-cased.
Wow, that is a nice motherboard. Thanks!

I was wondering meanwhile, that maybe it is possible to enable this feature on all uATX boards if the lanes are connected to the CPU, because in theory the CPU does most of the work here and Ryzen support x8/x8. Ofc. if there is no physical connection, then it is impossible to do it. I'll investigate this later.
 

doubletake

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Wow, that is a nice motherboard. Thanks!

I was wondering meanwhile, that maybe it is possible to enable this feature on all uATX boards if the lanes are connected to the CPU, because in theory the CPU does most of the work here and Ryzen support x8/x8. Ofc. if there is no physical connection, then it is impossible to do it. I'll investigate this later.

Well, that's the problem: most of the time they aren't, which is why they specify x4 being the max speed for those secondary x16 slots. I don't think there's a single mATX motherboard out there that has a secondary x16 slot that is actually wired to the CPU, but doesn't have x8/x8 support. It's all or nothing.
 

NattyKathy

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I went thru this search awhile ago trying to build a dual-GPU AM4 system in a uATX case and came up empty. All the boards I found had the second full-length PCIe slot coming off the Chipset, even the higher-end X470/570 ones. Some ASRock boards even have an option for bifurcation in the BIOS but it's only for splitting the top slot (with a riser I guess?) uATX mGPU setups are a niche within a niche and it's easier to connect the second slot to the chipset I guess, plus that arraignment can be better in situations where the second slot is occupied with something that's not bandwidth-sensitive because the GPU still gets its full 16 lanes.
 

inf3rno

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I went thru this search awhile ago trying to build a dual-GPU AM4 system in a uATX case and came up empty. All the boards I found had the second full-length PCIe slot coming off the Chipset, even the higher-end X470/570 ones. Some ASRock boards even have an option for bifurcation in the BIOS but it's only for splitting the top slot (with a riser I guess?) uATX mGPU setups are a niche within a niche and it's easier to connect the second slot to the chipset I guess, plus that arraignment can be better in situations where the second slot is occupied with something that's not bandwidth-sensitive because the GPU still gets its full 16 lanes.
I did some calculations with mITX + bifurcation riser card, and it would be at least $200 cheaper if I could go with uATX and 2x8 with two slots. It is very annoying that all manufacturers make small size + 2x8 some sort of challange or server feature and either I buy a server grade bifurcation riser card with PCIE cables and a special case for an extra $200 or I buy an uATX server motherboard that is usually $200 more expensive, than a consumer grade one. I don't even know where to buy a server board in my country, most of them are sold to companies, not to consumers and there are not many server boards for AM4 if there is any, because it is a consumer CPU e.g. ECC is not validated in it. I might go with Intel s1200 or s1151 instead depending on my CPU needs. Those boards at least exist (e.g. MSI MPG Z490M GAMING EDGE WIFI or ASUS TUF Z390M-PRO GAMING). It is really bad that this feature could be easily supported by manufacturers, but they don't care or they intentionally don't implement them.
 
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