Any AM5 Motherboards Capable of 16x/8x slots irrespective of gen?

[Zarathustra[H]]

Has anyone seen anything like this?

I'm trying to see if I can make a non-hedt system actually work for me.

My minimum requirements are:

- At least one x16 slot (physically and electrically) Preferably Gen5 for future proofing, but Gen4 is fine as well, as I'll probably upgrade again before Gen5 is a must on graphics.

- At least one 8x slot (physically and electrically) Must be at least Gen2. Gen3+ preferable.

- At least one Gen5 x4 m.2 slot.

I understand this would require some sort of PLX chip. There is enough physical bandwidth if switched, but there are not enough physical lanes.

Has anyone seen a board like this?

Of the 28 PCIe Gen5 lanes I am picturing them being used something like this:

- 16x straight to the GPU slot.
- 4x straight to the primary m.2 slot
- 4x straight to the chipset

This leaves 4x Gen5, which has enough bandwidth to be switched down to 8x Gen4 or lower.

A secondary 4x Gen 4 m.2 slot could come off the chipset.

I have googled, but I have not come across this configuration yet. If anyone has seen one, I'd appreciate the info!

 

[pendragon1]

afaik most full size atx x670 boards with 2 full size pcie slots will do that. can you just put your x8 card in the "16" slot? and another afiak, no ones using plx chips anymore, not for a while.
edit: maybe im wrong, im now seeing that most flip to x8 if both slots are used. huh....

 

[chameleoneel]

Has anyone seen anything like this?

I'm trying to see if I can make a non-hedt system actually work for me.

My minimum requirements are:

- At least one x16 slot (physically and electrically) Preferably Gen5 for future proofing, but Gen4 is fine as well, as I'll probably upgrade again before Gen5 is a must on graphics.

- At least one 8x slot (physically and electrically) Must be at least Gen2. Gen3+ preferable.

- At least one Gen5 x4 m.2 slot.

I understand this would require some sort of PLX chip. There is enough physical bandwidth if switched, but there are not enough physical lanes.

Has anyone seen a board like this?

Of the 28 PCIe Gen5 lanes I am picturing them being used something like this:

- 16x straight to the GPU slot.
- 4x straight to the primary m.2 slot
- 4x straight to the chipset

This leaves 4x Gen5, which has enough bandwidth to be switched down to 8x Gen4 or lower.

A secondary 4x Gen 4 m.2 slot could come off the chipset.

I have googled, but I have not come across this configuration yet. If anyone has seen one, I'd appreciate the info!

In theory, X670 should be capable. And so should B650E (however, there aren't many of those yet. and the pricing doesn't make sense.)

 

[Zarathustra[H]]

afaik most full size atx x670 boards with 2 full size pcie slots will do that. can you just put your x8 card in the "16" slot? and another afiak, no ones using plx chips anymore, not for a while.
edit: maybe im wrong, im now seeing that most flip to x8 if both slots are used. huh....

Well, the PLX brand was absorbed by Broadcom, but PCIe switches are still a thing.

I just kind of got so used to calling them PLX chips. I guess it's like a Kleenex or a Bandaid.

The Microchip Switchtec PM5xxxx series seems to have been around for a surprisingly long time. They seem like a plausible option for motherboard makers to lean on.

Yeah that's what I'm seeing too. 16x/0x or 8x/8x

It's a shame.

 

[lopoetve]

Well, the PLX brand was absorbed by Broadcom, but PCIe switches are still a thing.

I just kind of got so used to calling them PLX chips. I guess it's like a Kleenex or a Bandaid.

The Microchip Switchtec PM5xxxx series seems to have been around for a surprisingly long time. They seem like a plausible option for motherboard makers to lean on.

Yeah that's what I'm seeing too. 16x/0x or 8x/8x

It's a shame.

Trick is that nothing really needs the x16 full speed - not even GPUs (that I've seen, unless there are new benchmarks out - even Gen4 wasn't bottlenecked at x8).

PLX chips cost a LOT now - the only recent board I know of with one on it is from Supermicro (https://www.tomshardware.com/news/supermicro-c9z490-pgw-z490-motherboard-comet-lake) - and it's old. You're gonna be stuck praying for HEDT like me.

 

[bwang]

What do you need an electrical x16 for? I can't imagine a single instance where putting a GPU in a x16 slot made it faster, and I feel if you have a x8 5.0 slot you'll survive until the platform is obsolete.

 

[Zarathustra[H]]

What do you need an electrical x16 for? I can't imagine a single instance where putting a GPU in a x16 slot made it faster, and I feel if you have a x8 5.0 slot you'll survive until the platform is obsolete.

I'd agree that 8x Gen5 would be more than enough bandwidth for any GPU currently on the market.

The problem is, you can't get 8x gen5 bandwidth, unless both the GPU and the CPU support gen5.

There are currently no Gen5 GPU's on the market.

So, if your GPU is 16x Gen4, and your motherboard is providing 8x Gen5, they will auto-negotiate at the lowest common denominator for both sides, which is 8x Gen4.

8x Gen4 may still be sufficient, but it is getting uncomfortably close IMHO, and I'd rather have the peace of mind of having 16x available. Otherwise any time I ahve a little stutter, I am going to be questioning if I made a mistake, and if that was because 8x Gen4 wasn't sufficient.