Question PCI(e) compatibility

[Cameron231099]

Heyo. Haven't built a system in a long time and looking to upgrade.

Currently stuck on the motherboard of all things though, as the PCI(e) generations are confusing me.
Chipsets like the B350 are listed as PCIe gen2 yet the listings of actual B350 motherboards are stating it's using PCIe gen3?

Pulling my hair out trying to figure out what works with what in terms of PCIe lanes, any info on this current build would be appreciated. Thanks in advance.

 

[drea.drechsler]

Heyo. Haven't built a system in a long time and looking to upgrade.

Currently stuck on the motherboard of all things though, as the PCI(e) generations are confusing me.
Chipsets like the B350 are listed as PCIe gen2 yet the listings of actual B350 motherboards are stating it's using PCIe gen3?

Pulling my hair out trying to figure out what works with what in terms of PCIe lanes, any info on this current build would be appreciated. Thanks in advance.

The reason for the confusion is some PCIe sockets are fed by the CPU and some by the chipset. CPU's feed the GPU and first M.2 NVME, the chipset feeds the rest of the PCIe sockets. CPU's and chipsets have different generational capabilities depending on generation and model of each.

1000 and 2000 series CPU's offer gen 3 to all AM4 motherboards, 3000 and 5000 offer gen 4 to only B550 and X570 motherboards.

B350 motherboards can only support Gen 3 on GPU regardless of the CPU and the first NVME M.2, gen 2 from the chipset to all other PCIe sockets.

PCIe is forwards and backwards compatible: it will negotiate the highest gen both the device and the host can support.

So with a 3900X CPU and B350 pro 4 motherboard... the CPU will be limited to gen 3 to the GPU and NVME M.2 socket. The B350 chipset will provide gen 2 to all other PCIe sockets.

Some unasked-for advice, take it for what it's worth. With a proper BIOS update that board/CPU combination will work but probably not well. B350 motherboards on the whole had fairly weak VRM's and a 3900X (12 core/24 thread) is a power hungry beast of a CPU. It's just not a good combination.

Of course, you're also throwing away it's Gen 4 bandwidth to the GPU but that's never been shown to be such a major benefit. Unless running something like an RX 6500 XT with 4 lanes max of PCIe.

 

[--SID--]

In a B350 motherboard the upper PCI-e x16 slot is connected to the CPU and will run at max PCI-e3.0. On your motherboard all other PCI-e slots are connected to the chipset and are running at PCI-e2.0.

 

[Nighthawk117]

Heyo. Haven't built a system in a long time and looking to upgrade.

Currently stuck on the motherboard of all things though, as the PCI(e) generations are confusing me.
Chipsets like the B350 are listed as PCIe gen2 yet the listings of actual B350 motherboards are stating it's using PCIe gen3?

Pulling my hair out trying to figure out what works with what in terms of PCIe lanes, any info on this current build would be appreciated. Thanks in advance.

I don't know what your budget is like, but you would be much better off with a B550 board with a Zen 2 or 3 CPU. Any reason for the 3900X, the 5900X is cheaper and significantly better at high refresh rate gaming:
https://www.scan.co.uk/products/amd...59aQ6S1zXZwcBrvDhaOva6AY9fKzwHpcaAqggEALw_wcB

The Hyper 212 is also barely adequate for a Ryzen 9. I would recommend a 240mm AIO liquid cooler or a large tower cooler like a NH-D15.

 

[Cameron231099]

The reason for the confusion is some PCIe sockets are fed by the CPU and some by the chipset. CPU's feed the GPU and first M.2 NVME, the chipset feeds the rest of the PCIe sockets. CPU's and chipsets have different generational capabilities depending on generation and model of each.

1000 and 2000 series CPU's offer gen 3 to all AM4 motherboards, 3000 and 5000 offer gen 4 to only B550 and X570 motherboards.

B350 motherboards can only support Gen 3 on GPU regardless of the CPU and the first NVME M.2, gen 2 from the chipset to all other PCIe sockets.

PCIe is forwards and backwards compatible: it will negotiate the highest gen both the device and the host can support.

So with a 3900X CPU and B350 pro 4 motherboard... the CPU will be limited to gen 3 to the GPU and NVME M.2 socket. The B350 chipset will provide gen 2 to all other PCIe sockets.

Some unasked-for advice, take it for what it's worth. With a proper BIOS update that board/CPU combination will work but probably not well. B350 motherboards on the whole had fairly weak VRM's and a 3900X (12 core/24 thread) is a power hungry beast of a CPU. It's just not a good combination.

Of course, you're also throwing away it's Gen 4 bandwidth to the GPU but that's never been shown to be such a major benefit. Unless running something like an RX 6500 XT with 4 lanes max of PCIe.

Cheers, this makes PCIe more understandable to layman such as myself . Just been reading more reviews on the B350 series and I'll probably go with something more modern as you suggested.

I don't know what your budget is like, but you would be much better off with a B550 board with a Zen 2 or 3 CPU. Any reason for the 3900X, the 5900X is cheaper and significantly better at high refresh rate gaming:
https://www.scan.co.uk/products/amd...59aQ6S1zXZwcBrvDhaOva6AY9fKzwHpcaAqggEALw_wcB

The Hyper 212 is also barely adequate for a Ryzen 9. I would recommend a 240mm AIO liquid cooler or a large tower cooler like a NH-D15.

A 3900x is 205 GBP used, where as a 5900x is 310 GPB used (>50% more expensive). Trying to get the best price-performance. I will look into a better cooler though, but a liquid cooler is just too much of an expense and hassle for me right now.

 

[Nighthawk117]

A 3900x is 205 GBP used, where as a 5900x is 310 GPB used (>50% more expensive). Trying to get the best price-performance. I will look into a better cooler though, but a liquid cooler is just too much of an expense and hassle for me right now.

Fair enough that makes more sense now.

 

[drea.drechsler]

....
A 3900x is 205 GBP used, where as a 5900x is 310 GPB used (>50% more expensive). Trying to get the best price-performance. I will look into a better cooler though, but a liquid cooler is just too much of an expense and hassle for me right now.

That's a fair trade if your processing needs cores and threads for performance. But if just for gaming you might look at a 5600X...or even 5600 CPU. They should run a good deal cheaper than a 5900X and run most any game as well...or better...than a 3900X. Games are generally lightly threaded and don't need cores but they do like higher single thread performance and 5000 series CPU's provide that.

Not sure how prices compare in your region though.

 

[Cameron231099]

That's a fair trade if your processing needs cores and threads for performance. But if just for gaming you might look at a 5600X...or even 5600 CPU. They should run a good deal cheaper than a 5900X and run most any game as well...or better...than a 3900X. Games are generally lightly threaded and don't need cores but they do like higher single thread performance and 5000 series CPU's provide that.

Not sure how prices compare in your region though.

5600x/5600 are pretty competitive, but at least in terms of render scores for r23 cinebench the 5900x is better price/performance ratio compared to 5600x/5600. 5600 would be better just for raw gaming tho probably, as you said, but I am mainly upgrading for the render performance

Thanks for the replies all, i've updated my mobo to an Asus PRIME B450-PLUS on the back of the advice regarding B350s, and since decent tower coolers are kinda expensive anyways i've just found a second hand Cooler Master MasterLiquid ML240L V2 that should last me pretty much forever.