Need 16x-8x configuration at same time. Are there any consumer boards?

Zarathustra[H]

Zarathustra[H]

Extremely [H]
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As in title.

I am looking for an LGA1700 or AM5 motherboard that allows me to have a GPU at 16x and a second slot at 8x at the same time.

All of them I can find degrade the primary CPU slot down to 8x when you use the second slot. I want 16x-8x with both slots populated, not 8x-8x.

I would like main GPU slot to be gen 5 (for future proofing) but Gen4 would be acceptable. I don't care if the secondary 8x slot is an older gen. As long as it is Gen3 or faster.

LGA1700 only has 20 lanes, so I think that not going to happen (but they are gen5, so you never know with PCIe switches)

AM5 has 28 lanes, so it should be theoretically possible, even with all gen5, with 4 lanes to spare (for m.2 or chipset or whatever)

Has anyone ever seen a motherboard with this kind of 16x-8x configuration? I have spent hours pouring through Neweggs filters trying to find one with no success.

There has to be at least one... Right?

Yes, I know there are Xeon and Threadripper boards that do this, but they all have serious compromises affecting their client/gaming performance (and are increasingly unaffordable) so they are straight out.

I'd appreciate any suggestions.
 
I haven't seen any available on AM5 / LGA 1700. An RTX 4090 only loses about 2% - 3% performance depending on the resolution when you run it at PCIe 4.0 x8. So if you really need that second x8 slot on a consumer platform you'll have to eat the performance loss on your GPU. I would probably speculate a PCIe 5.0 x8 slot will maybe even lessen that difference once we see PCIe 5.0 GPUs.
 
Man. This drives me up a freaking wall.

All the lanes are there, but they decided to give us one 4x slot and four 1x slots instead of an 8x slot....

1710794980542.png

1710794993455.png


It makes me want to scream.
 
Another one... All the necessary lanes are there, but two 4x slots instead of one 8x slot....

1710795393444.png


It's like they are intentionally trying to stop me from ever upgrading.
 
Supermicro is in on it too.

Their consumer CPU based X13SAE line has two Gen3 X4 slots instead of one Gen3 8x slot...
 
I'm actually starting to think that is the case.

That Intel is preventing the board makers from offering secondary 8x slots that don't impact the 16x GPU slot in order to not cannibalize their Xeon line...

I mean, otherwise the absence of these slots just seems to odd to be true. Almost any power user has eye-balled workstation/server parts like NIC's and SAS HBA's and they are almost always 8x for some reason. If they were truly trying to satisfy the Pro-Sumer market they would be trying to include that ability.

I haven't seen any AMD offerings with sufficient lanes but in useless configurations yet, so on AMD there may actually be a technical/chipset limitation.

I've got my fingers crossed that Zen5 will come with a new chipset that allows for an 8x Gen3+ slot off of the chipset. Otherwsie I guess I'm just going to continue using this aging Threadripper forever I guess.
 
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Think Asrock's B650 Pro RS is about as close as you'll get:

CPU:
- 1 x PCIe 4.0 x16 Slot (PCIE1), supports x16 mode*
- 1 x PCIe 3.0 x16 Slot (PCIE3), supports x4 mode*
Chipset:
- 1 x PCIe 4.0 x1 Slot (PCIE2)*
- 1 x M.2 Socket (Key E), supports type 2230 WiFi/BT PCIe WiFi module
- Supports AMD CrossFire™
- 15μ Gold Contact in VGA PCIe Slot (PCIE1)
Click to expand...
 
Nobu said:
Think Asrock's B650 Pro RS is about as close as you'll get:
Click to expand...

I guess I'm just going to have to wait then.

Until I can find a motherboard that both boasts top tier consumer CPU performance in low threaded workloads AND allows me full one full 16x (gen 4+) and one full 8x (gen3+) electrically, at the same time I'm just not going to upgrade.

I was ready to jump on the new Threadrippers, but unlike the 3xxx series, the performance is just terrible in non-workstation loads wjhen compared to their consumer counterparts.

Fingers crossed Zen5 and its associated new chipset brings more options along this line. They could start by bumping up the chipset links to actually support Gen5 instead of Gen4, which should provide enough bandwidth to offer some more flexibility to Motherboard designers.
 
Nobu said:
What do you need the second 8x slot for?
Click to expand...

I have a networking setup that depends on a discrete NIC that is 8x Gen3 which I am totally committed to.

I want to upgrade, but if it means I have to remove my network setup, then I'm just going to pass.
 
PCIe 4.0 x4 is theoretically the same bandwidth as 3.0 x8, right?

Are you sure that X16 slot #22 doesn't allow an x8 multiplier, if the connected hardware is PCIe 3.0?
 
chameleoneel said:
PCIe 4.0 x4 is theoretically the same bandwidth as 3.0 x8, right?

Are you sure that X16 slot #22 doesn't allow an x8 multiplier, if the connected hardware is PCIe 3.0?
Click to expand...

That would require a PLX or other PCIe switch. These are built into the chipset (or they wouldn't be able to that those 4 lanes that come in from the CPU and turn them into all these other things on the other side) but I have never seen one operate the way you suggest. If it did, they would probably brag about it in the specs, as adding that type of PCIe Switching capacity wouldn't be cheap. They are surprisingly expensive little chips.

Usually the way it works is you get the lowest gen of the add-on board and motherboard, and the lowest number of lanes of the add-on board and motherboard.

So, if the motherboard claims 4x Gen 4 and the PCIe add-on board claims 8x Gen 3, it will auto-negotiate 4x Gen 3, and that's it.
 
I can tell you what I did to preserve my x16 GPU and then have my 10gbe card...not that it is of any help...

I found a 10gbe networking card that used a spare m.2. I had to order it from good ol' ali express, but it works...well, when I got a proper cooler for it.
 
applegrcoug said:
I can tell you what I did to preserve my x16 GPU and then have my 10gbe card...not that it is of any help...

I found a 10gbe networking card that used a spare m.2. I had to order it from good ol' ali express, but it works...well, when I got a proper cooler for it.
Click to expand...
If a single 10gig port were all I needed, I'd just use the on board port of a fancy motherboard.

Right now I have a dual QSFP+ card in my workstation. I could technically get away with just a dual port SFP28 card, but I haven't seen any of those in 4x either.
 
Why do you need that machine to handle the networking? Could you throw another PC into your network that does that part of the lifting?
 
Axman said:
Why do you need that machine to handle the networking? Could you throw another PC into your network that does that part of the lifting?
Click to expand...

I do a lot of concurrent storage stuff over the network from my desktop.

I am unable to max out the 40Gbit NIC (though it was fun to try) but I can definitely get above 10Gbit, so a 10gig connection is just not enough.
 
Zarathustra[H] said:
I do a lot of concurrent storage stuff over the network from my desktop.

I am unable to max out the 40Gbit NIC (though it was fun to try) but I can definitely get above 10Gbit, so a 10gig connection is just not enough.
Click to expand...

Right, so why is your desktop the server?
 
Axman said:
Right, so why is your desktop the server?
Click to expand...

It isn't.

It's the client.

I'll often be doing many different things at the same time from my desktop. Editing a video saved remotely, playing something else from my NAS for background noise, imaging a drive to the server, doing a massive file search on the server, trans-coding something in the background, transferring a drive image to a VM, etc. etc.

These things are not always going to happen at the same time, but they do often enough that I want to make absolutely sure that my bandwidth to the server is not the limiting factor. And when working across multiple storage pools, some spinning rust, but some also NVMe, and even RAM disks, it puts a lot of demand on the network.

I am almost constantly hammering the network when I am using the machine, and I would be unhappy if I had to go back to just 10gig.
 
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Zarathustra[H] said:
If a single 10gig port were all I needed, I'd just use the on board port of a fancy motherboard.

Right now I have a dual QSFP+ card in my workstation. I could technically get away with just a dual port SFP28 card, but I haven't seen any of those in 4x either.
Click to expand...

Could you get that board with x16 (for GPU) and two x4s and a second NIC? Use half the ports on each NIC?

It's derpy, but I think it solves your problem? Maybe the cost is too high still though.
 
Zarathustra[H] said:
I guess I'm just going to have to wait then.

Until I can find a motherboard that both boasts top tier consumer CPU performance in low threaded workloads AND allows me full one full 16x (gen 4+) and one full 8x (gen3+) electrically, at the same time I'm just not going to upgrade.

I was ready to jump on the new Threadrippers, but unlike the 3xxx series, the performance is just terrible in non-workstation loads wjhen compared to their consumer counterparts.

Fingers crossed Zen5 and its associated new chipset brings more options along this line. They could start by bumping up the chipset links to actually support Gen5 instead of Gen4, which should provide enough bandwidth to offer some more flexibility to Motherboard designers.
Click to expand...
I highly doubt you'll ever see a consumer board support what you want (at least in the somewhat near future). Hopefully future HEDT/Server platforms tickle your fancy because that's likely the only way you'll get simultaneous x16/x8. What you're looking for is incredibly niche for a typical consumer platform. I don't think Intel or AMD or any board vendors see a point in making a platform or board like this for consumers.

Zarathustra[H] said:
I am unable to max out the 40Gbit NIC (though it was fun to try) but I can definitely get above 10Gbit, so a 10gig connection is just not enough.
Click to expand...

A PCIe 3.0 x4 slot can deliver 4GB/s bandwidth, theoretically giving you up to 32Gbps for your QSFP+ NIC. Wouldn't that suit your needs just fine? It might not reach that full theoretical speed but I'd expect to be somewhat close. Hopefully soon we'll see PCIe 4.0 x4 NICs come out since this is the same bandwidth as PCIe 3.0 x8 and that will invalidate your need for the mythical x16/x8. Or... simply eat a 2% - 3% performance loss on your GPU to run x8/x8; which is a perfectly acceptable trade-off to get very high speed networking on a consumer platform.
 
Dopamin3 said:
A PCIe 3.0 x4 slot can deliver 4GB/s bandwidth, theoretically giving you up to 32Gbps for your QSFP+ NIC. Wouldn't that suit your needs just fine?
Click to expand...

He's got a dual port QSFP+ ... 32Gbps pci-e bandwidth for 80Gbps network bandwidth is pretty meh.
 
I've spent way too much time looking at this one. i think you're not going to find what you want until they come out with a new generation of network cards that run PCIe Gen4x4 instead of PCIe Gen3x8. Until then, something is going to get throttled back....GPU if it runs x8, network card if it runs x4, wallet if it buys a threadripper.
 
cyclone3d said:
Look at the ASUS workstation boards that have PLX chips in them.

The boards are expensive but will do what you want.

https://www.asus.com/us/motherboards-components/motherboards/all-series/filter?Series=Workstation
Click to expand...

I'm looking at those, and the only ones that have 16x-8x (at the same time) capability are The Threadripper, EPYC and Xeon boards. None of the consumer ones.

As an example, here is the Pro WS W680-ACE IPMI:
1712075891357.png


Stick any card in the second slot, and the 16x slot drops down to 8x, which is unacceptable to me.

Frustratingly enough there are two 4x Gen3 slots instead of one 8x slot. So the lanes are there and usable, they just refuse to configure them so I can use an 8x card.
 
Uggghhhh, what happened to them making workstation boards that have PCIe switches on them that don't require the XEON or Threadripper?

I've got a couple older ones that do and they are great if you need lots of PCIe lanes.
 
cyclone3d said:
Uggghhhh, what happened to them making workstation boards that have PCIe switches on them that don't require the XEON or Threadripper?

I've got a couple older ones that do and they are great if you need lots of PCIe lanes.
Click to expand...
toast0 said:
PCIe switches got real expensive.
Click to expand...
toast0 said:
PCIe switches got real expensive.
Click to expand...

Yeah. Ever since Broadcom cornered the market by buying PLX Technology, prices for these things have been kind of ridiculous.

They aren't the only player. There are others (like Microchip Technology) but there isn't enough real competition to keep pricing reasonable like it used to be prior to 2014.

The exception is in Motherboard Chipsets.

Just about every Intel and AMD chipset in the last 15 years has some sort of integrated PCIe switching to enable them to feed off a small number of latest gen PCIe lanes from the CPU and use them to branch out to all the on board devices and Chipset PCIe lanes going to m.2 and PCIe slots. They are the exception due to their comparatively extremely high production volumes, but they are also rather limited in their capability compared to the standalone implementations.

I am hopeful that the next Chipset from AMD to support Zen5 will do better and allow me to get what I want. Current Chipsets use four lanes but only in Gen4 mode. If they up those to the Gen 5 the CPU supports there will be a boatload of available bandwidth on the Chipset side. Four gen 5 lanes have the bandwidth of ~16 Gen3 lanes, or ~32 Gen2 lanes.

That could really change some things.

But I have also been disappointed many chipsets in a row, so I am not quite holding my breath.

The Threadripper 3960x is still capable enough for what I need ti to do, but I am not going to lie. Having a little more low threaded performance from a newer arch would be nice, and thus the urge to upgrade is there.

I was just disappointed in the performance of the Threadripper 7000 series and Intel's Workstation Xeons. They are great workstation CPU's but in lightly threaded loads the performance just falls apart. My best guess is a lot of this has to do with DDR5. With DDR4 Registered and unregistered DIMM's were pin compatible, and motherboards and CPU's could be designed to allow both on the same system, giving the user the choice of building something more HEDT like (like what I want) with unregistered DDR4 or more workstation like with Registered DDR4.

These days - however - Registered and unregistered DDR5 are not pin compatible. Because of this, modern Threadrippers and Xeon's use Registered DDR5 and are thus more workstation like, and less HEDT-like.

I want a top tier consumer CPU with its top tier lightly threaded performance, while also having enough PCIe lanes to give me more flexibility like I get from my Threadripper.

If I can get 16x and 8x at the same time from a consumer board, I will get pretty close. That is my hope.
 
According to bingGPT the z790-e could possibly, if you do not mind the x8 to go to the chipset and not the cpu (the mention gen3 or faster indicating that it could be acceptable) and not use the m2_1 5.0 to the cpu:

https://www.techreviewer.com/tech-answers/best-lga-1700-motherboard/

1x16 or 2x8 PCI-e 5.0 to the cpu
1x8 PCI 4.0

This for example if is not misleading
https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/
1x16 (5.0) + 2x16 (4.0) chipset

https://www.tech-critter.com/asus-rog-strix-z790-e-gaming-wifi-review/
Intel 13th Gen Processors: 1 x PCIe 5.0 x16 slots
Intel Z790 Chipset: 2 x PCIe 4.0 x16 slots, 1 x PCIe 3.0 x1 slot

If you use the m.2_1 slot the x16 of the pci 5.0 goes down to x8, I imagine there is a catch somewhere but cannot find it there:
https://www.manualslib.com/manual/3078771/Asus-Rog-Strix-Z790-E-Gaming-Wifi.html?page=7#manual
 
LukeTbk said:
According to bingGPT the z790-e could possibly, if you do not mind the x8 to go to the chipset and not the cpu (the mention gen3 or faster indicating that it could be acceptable) and not use the m2_1 5.0 to the cpu:

https://www.techreviewer.com/tech-answers/best-lga-1700-motherboard/

1x16 or 2x8 PCI-e 5.0 to the cpu
1x8 PCI 4.0

This for example if is not misleading
https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/
1x16 (5.0) + 2x16 (4.0) chipset

https://www.tech-critter.com/asus-rog-strix-z790-e-gaming-wifi-review/
Intel 13th Gen Processors: 1 x PCIe 5.0 x16 slots
Intel Z790 Chipset: 2 x PCIe 4.0 x16 slots, 1 x PCIe 3.0 x1 slot

If you use the m.2_1 slot the x16 of the pci 5.0 goes down to x8, I imagine there is a catch somewhere but cannot find it there:
https://www.manualslib.com/manual/3078771/Asus-Rog-Strix-Z790-E-Gaming-Wifi.html?page=7#manual
Click to expand...
According to this, the second slot will be either 8x+4x+4x (bifurcated) or 8x. Don't ask me why, but at least it's better than 4x.

Edit: The XII Hero (wifi) and the pro ws w480 ACE are the same.
 
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Now that an expensive enough board (near $400) to maybe not be that much of a rebate over the cheaper Xeon entry.... but maybe there is some non Republic of gamer version of z790-e that does it has well.


If the x16 for the GPU is only a future GPU gaming matter (thinking that it will not be a pci5 and will be impacted by x8 in some scenario like a used 4090 maybe... ? but maybe video editing use that bandwith with the gpu.. ?), going with a different PC for gaming than work could be intuitively a cheaper route.... 5800x3d/7800x3d on a cheap board because does not really matter and the work one that does not need to stress for a super GPU, connection to it get simpler. (maybe keeping the current workstation on the network to make it do the trans-coding type of work.

The older Intel extreme type that do both at the same time is maybe less available right now
 
LukeTbk said:
According to bingGPT the z790-e could possibly, if you do not mind the x8 to go to the chipset and not the cpu (the mention gen3 or faster indicating that it could be acceptable) and not use the m2_1 5.0 to the cpu:

https://www.techreviewer.com/tech-answers/best-lga-1700-motherboard/

1x16 or 2x8 PCI-e 5.0 to the cpu
1x8 PCI 4.0

This for example if is not misleading
https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/
1x16 (5.0) + 2x16 (4.0) chipset

https://www.tech-critter.com/asus-rog-strix-z790-e-gaming-wifi-review/
Intel 13th Gen Processors: 1 x PCIe 5.0 x16 slots
Intel Z790 Chipset: 2 x PCIe 4.0 x16 slots, 1 x PCIe 3.0 x1 slot

If you use the m.2_1 slot the x16 of the pci 5.0 goes down to x8, I imagine there is a catch somewhere but cannot find it there:
https://www.manualslib.com/manual/3078771/Asus-Rog-Strix-Z790-E-Gaming-Wifi.html?page=7#manual
Click to expand...

Not sure I trust AI summaries. I prefer to verify manually the old fashioned way to be sure.

When I do, the Asus Rog Z790e specs page suggests it has one 16x Gen5 slot and two 4x Gen 4 slots off the chipset.

If those two x4 slots could be combined to a single 8x slot, that would be great, but I see nothing that suggests that is possible anywhere.
 
Zarathustra[H] said:
The Asus Rog Z790e spcs page suggests it has one 16x Gen5 slot and two 4x Gen 4 slots off the chipset.
Click to expand...
WHich page is that, cannot find anything anywhere that went below giving you at least 1x8 (are you sure it is not when you use the m2_1 slot ?)
 
LukeTbk said:
WHich page is that, cannot find anything anywhere that went below giving you at least 1x8 (are you sure it is not when you use the m2_1 slot ?)
Click to expand...
On the official Asus product page, click specs, takes you here:

https://rog.asus.com/motherboards/rog-strix/rog-strix-z790-e-gaming-wifi-model/spec/

Scroll down to "Expansion Slots" and you will find:

Code: 
Expansion Slots
 
 Intel® 13th & 12th Gen Processors
1 x PCIe 5.0 x16 slot

Intel® Z790 Chipset
2 x PCIe 4.0 x16 slots (support x4 mode)

* Please check the PCIe bifurcation table
on the support site (https://www.asus.com/support/FAQ/1037507/).
** When M.2_1 is occupied with SSD device, PCIEX16(G5) will run x8 only.
*** To ensure compatibility of the device installed, please refer to https://www.asus.com/support/ for the list of supported peripherals.
 
Nobu said:
According to this, the second slot will be either 8x+4x+4x (bifurcated) or 8x. Don't ask me why, but at least it's better than 4x.

Edit: The XII Hero (wifi) and the pro ws w480 ACE are the same.
Click to expand...
Zarathustra[H] said:
Not sure I trust AI summaries. I prefer to verify manually the old fashioned way to be sure.

When I do, the Asus Rog Z790e specs page suggests it has one 16x Gen5 slot and two 4x Gen 4 slots off the chipset.

If those two x4 slots could be combined to a single 8x slot, that would be great, but I see nothing that suggests that is possible anywhere.
Click to expand...
The manual refers specifically to the table on the page I linked to above. If that's wrong, there'll be a lot of angry users who can't use all their m2 drives at full speed.
 
Nobu said:
The manual refers specifically to the table on the page I linked to above. If that's wrong, there'll be a lot of angry users who can't use all their m2 drives at full speed.
Click to expand...

Yeah, that link is on the spec page as well, but note that it addresses every motherboard under the sun, and has different supported configurations for each.

Their nomenclature is confusing, but I don't interpret this as supporting botjh a 16x GPU (in 16x mode) AND an 8x slot at the same time.

Here is how I read this table.

You can have 1 16x card in slot 1 --OR-- one 8x in slot one and one 8x in slot two.

1712084022950.png



Like this from the product page:

1712084306524.png
 
There are a couple EVGA boards that do PCIe 5.0 x8/x8 when both slots are populated.

Most other boards I am seeing only have a single PCIe 5.0 slot and the rest being 4.0
 
Zarathustra[H] said:
Yeah, that link is on the spec page as well, but note that it addresses every motherboard under the sun, and has different supported configurations for each.

Their nomenclature is confusing, but I don't interpret this as supporting botjh a 16x GPU (in 16x mode) AND an 8x slot at the same time.

Here is how I read this table.

You can have 1 16x card in slot 1 --OR-- one 8x in slot one and one 8x in slot two.

View attachment 645312


Like this from the product page:

View attachment 645313
Click to expand...
Slot two ("G5") is supposed to support one x16 or two x8 (bifurcated, so you'll need a riser/adapter card). What's not clear is whether it supports bifurcation when slot one is occupied...I'm afraid it doesn't, but it's really not made clear anywhere.

Edit: Actually looks like "G5" is often slot 1, but sometimes slot 2. So maybe the board where it's slot 2 supports 16x in both. Gotta check.

Nope, those show 8x or 0x (huh?). :/
 
Nobu said:
Slot two ("G5") is supposed to support one x16 or two x8 (bifurcated, so you'll need a riser/adapter card). What's not clear is whether it supports bifurcation when slot one is occupied...I'm afraid it doesn't, but it's really not made clear anywhere.

Edit: Actually looks like "G5" is often slot 1, but sometimes slot 2. So maybe the board where it's slot 2 supports 16x in both. Gotta check.

Nope, those show 8x or 0x (huh?). :/
Click to expand...

Yeah, they really don't make interpreting PCIe lane configurations easy.

Been that way as long as I can remember. Every time I have upgraded in the PCIe era I have found myself pouring over motherboard specs and thinking "well, that sure is ambiguous".
 
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