PCIE Gen 4 confusion

[BlaezaLite]

I'm sure that the R5 3600 and MSI b450m mortar max don't support PCIE Gen 4, but they are both reporting as supporting it in hwinfo. I'm very confused. I did a bios update in 2021 so can that change the PCIE Generation or am I just showing I know nothing about PCs?

 

[AusWolf]

The 3600 supports gen 4, but B450 boards don't, as far as I know. Hwinfo might have got confused by the 3600, I think. You won't know for sure until you pop a gen 4 graphics card in it.

 

[BlaezaLite]

Hmmm... Thank you for correcting me about the 3600, but I'm sure the mobo is gen 3, it says so on the MSI website. Or can you update gen 3 mobo's to gen 4? I live to be confused I swear.

 

[TheLostSwede]

Some B450/X470 boards are in theory PCIe 4.0 capable and there were some beta UEFI releases that were circulating that enabled PCIe 4.0 support. However, as not all boards could do PCIe 4.0, AMD decided that none of them would be allowed to do it, to reduce consumer confusion or to favour certain board makers/models.

 

[qubit]

Don't feel too bad about feeling confused, especially so when you get conflicting information.

Now, without looking at the specifics of your hardware, I can still give you some general information.

The PCIe generation is set by the capabilities of the hardware, ie the hardware must be designed to support later versions. The speed so far doubles every generation, so this isn't a small upgrade, either. You can't just overclock current hardware to get to the next level. There are formal technical standards that PCIe adheres to, to support the various generations, see the official website below.

It's possible for a gen 4 board to be sold with an early bios that only supports gen 3 for various technical and / or marketing reasons. Later on, the manufacturer makes available an updated bios to support gen 4. Boards like this should be sold as "PCIe 4 ready", or something like that. Note that a chipset that supports a later version, will be backwards compatible with the earlier ones and can likely be set to work in that mode via a register rather than only by detecting an earlier gen card plugged into the board. Whether that setting is exposed in the bios depends on the board manufacturer and enthusiast level of the product.

Therefore, it's quite possible that a hardware monitoring app could get confused over what the actual supported PCIe gen level is. It's quite possible that the app correctly recognizes gen 4 hardware, but misses the gen 3 bios that prevents it from working in gen 4 mode, giving conflicting results.

The official website for PCIe is here:

Welcome to PCI-SIG | PCI-SIG

pcisig.com

Hope this helps.

 

[Bill_Bright]

It should also be noted that PCIe 4.x is backwards compatible. You can put a 3.x card in a 4.x slot, or a 4.x card into a 3.x slot and "in theory" everything "should" work - just only at the slowest speeds supported.

So while HWiNFO may be reporting it is "supported", perhaps "compatible" is the better word.

 

[Z-GT1000]

PCIe 4.0 is only present in X570 chipset in all the rest of Ryzen chipset motherboards are only PCIe 3.0 compatible, the problem is when the Ryzen 3000 (Zen 2) arrived to the market one of the upgrades from Zen 1 a Zen+ are integrated PCIe 4.0 support in the I/O die of the cpu, all A320, B350, X370, B450, X470 support this direct PCIe 4.0 lines from the CPU for the PCIe_1 16x but AMD needs to sell B550 and X570 motherboards and made and agesa update blocking this option to manufacturers, if you have the correct bios you can have a PCIe 4.0 support in your B450 motherboard

 

[BlaezaLite]

Thanks for your explanations. I know that GPUs operate regardless of the pcie gen, just in the spec of the pcie slot.

PCIe 4.0 is only present in X570 chipset in all the rest of Ryzen chipset motherboards are only PCIe 3.0 compatible, the problem is when the Ryzen 3000 (Zen 2) arrived to the market one of the upgrades from Zen 1 a Zen+ are integrated PCIe 4.0 support in the I/O die of the cpu, all A320, B350, X370, B450, X470 support this direct PCIe 4.0 lines from the CPU for the PCIe_1 16x but AMD needs to sell B550 and X570 motherboards and made and agesa update blocking this option to manufacturers, if you have the correct bios you can have a PCIe 4.0 support in your B450 motherboard

Ooh, thats interesting! I'm going for a mooch to see if there is one available for my mobo!

 

[TheLostSwede]

Ooh, thats interesting! I'm going for a mooch to see if there is one available for my mobo!

I'd suggest you don't, as they were only ever beta versions and might be quite buggy if you find one.

 

[BlaezaLite]

I'd suggest you don't, as they were only ever beta versions and might be quite buggy if you find one.

Typical... Is there much to gain from having a pcie 4 board and pcie 4 GPU?

 

[TheLostSwede]

Typical... Is there much to gain from having a pcie 4 board and pcie 4 GPU?

See

NVIDIA GeForce RTX 3080 PCI-Express Scaling

NVIDIA Ampere finally brings PCI-Express 4.0 support to the high-end graphics market. The new interface promises twice the bandwidth of PCI-Express 3.0. We've setup an AMD Ryzen 3900XT system to test how various PCIe generations and lane widths affect gaming performance.

www.techpowerup.com

 

[looniam]

Typical... Is there much to gain from having a pcie 4 board and pcie 4 GPU?

nah just bandwidth:

Result

www.3dmark.com

Result

www.3dmark.com

Result

www.3dmark.com

psst, just examples, (different clk speeds ect) nothing more.

 

[Ruru]

With 8 and 16 lane cards, 3.0 is fine. With cards which have only 4 lanes, like RX 6400/6500 XT, then PCIe 4.0 gives advantage.

 

[BlaezaLite]

Thats still good news as I don't want either of them. What would be a good upgrade from my 1660 super? Gen 3 or 4 cards? I was thinking of amd 6600 or 2070 super, but I want a 50% increase in power without a £500 price tag.

 

[AusWolf]

Thats still good news as I don't want either of them. What would be a good upgrade from my 1660 super? Gen 3 or 4 cards? I was thinking of amd 6600 or 2070 super, but I want a 50% increase in power without a £500 price tag.

Both the 6600 and 2070 Super are good cards, though personally, I'd wait until next gen is out, and try to hunt for a good deal then. It's only a few months ahead.

 

[BlaezaLite]

Both the 6600 and 2070 Super are good cards, though personally, I'd wait until next gen is out, and try to hunt for a good deal then. It's only a few months ahead.

Aren't all the next gen cards pcie 5? But I do understand what you mean.

 

[AusWolf]

Aren't all the next gen cards pcie 5? But I do understand what you mean.

What I mean is, when the next gen is out, you may be able to score a good deal on current gen cards.

Like it was said above, pci-e generations don't matter on x16 and x8 cards. The only time it matters is on x4 which is currently the RX 6400 and RX 6500 XT only. Even with those, you're looking at a 10-15% performance difference at most, except for a few anomalies.

 

[Dr. Dro]

Aren't all the next gen cards pcie 5? But I do understand what you mean.

PCIe 5.0 only supported on Alder Lake right now, and there are no devices (graphics cards, NVMe SSDs, etc.) currently in the market, so that's not relevant at all at the present moment. But as it was said earlier, PCIe is both forwards- and backwards-compatible, you can use a PCIe 4.0 device on a PCIe 5.0 motherboard, and conversely you can use a PCIe 4.0 device on a PCIe 3.0 motherboard, as well. In fact, you're not limited to just one generation of back and forth, you can run a PCIe 1.0 graphics card on a PCIe 4.0 slot, i've done it before - an old 2006 vintage NVIDIA Quadro FX 5600 (same G80 core used on the GeForce 8800 GTX) with my R9 5950X machine. The available bandwidth will adjust itself automatically, negotiated between the host and the device

The AMD 300 and 400 series motherboards, as well as the A520 do not officially support PCIe 4.0, so with an updated BIOS, the feature will not be available even if used with a PCIe 4.0 compatible processor (Matisse Ryzen 3000X or Vermeer Ryzen 5000X), the APUs (Renoir 4000G and Cezanne 5000G) do not support 4.0 even on a 4.0 compatible motherboard. The chipsets that do are B550 and X570.

As far as graphics performance goes, it's also like mentioned earlier: GPUs that have x8 or x16 connections tend to run fine on 3.0, 4.0 is necessary only for the ones with x4 connections. AMD GPUs this generation tend to be more sensitive to PCIe bandwidth, and also the RTX 3080 Ti and 3090/Ti. Even the 3080 vanilla tends to be fine, it's not a big deal. This may change with the upcoming RDNA 3 and Ada Lovelace cards, so if you can keep more or less current with a 4.0 slot, that is desirable.
Hope it helps, cheers

 

[The King]

So I also noticed for some time that CPU-Z is showing PCI-e 4.0 support for my B450M Mortar Max
My current RX 480 only supports 3.0 x16.

Now If i wanted to get a PCie 4.0 x4 NVMe drive will the GPU cause a conflict with the Bus speeds?
I could move my GPU to the second PCI express slot on my board so that only the NVMe is connected directly to the CPU and not the GPU.
The GPU will then be connected to the B450 chipset but at x8.

Has anyone tried this on their B450 mobo?

 

[Dr. Dro]

So I also noticed for some time that CPU-Z is showing PCI-e 4.0 support for my B450M Mortar Max
My current RX 480 only supports 3.0 x16.

Now If i wanted to get a PCie 4.0 x4 NVMe drive will the GPU cause a conflict with the Bus speeds?
I could move my GPU to the second PCI express slot on my board so that only the NVMe is connected directly to the CPU and not the GPU.
The GPU will then be connected to the B450 chipset but at x8.

Has anyone tried this on their B450 mobo?

View attachment 268623

If you install a PCIe 4.0 GPU, it will run at 3.0 bus speeds. My brother's running an RTX 3070 on a B450M Steel Legend + R9 3900XT for almost 2 years now. Works fine.

 

[The King]

If you install a PCIe 4.0 GPU, it will run at 3.0 bus speeds. My brother's running an RTX 3070 on a B450M Steel Legend + R9 3900XT for almost 2 years now. Works fine.

I already have PCI-e 3.0x4 NVMe two WD SN570s. The main reason I never went with a 4.0x4 drive is because I thought I was limited to PCIe 3.0.

There are several articles online that shows the B450 can support 4.0 speeds and I don't mean that it backwards compatible. I mean performs like a 4.0 x4 NVMe should.

If its going to drop to 3.0 x4 then there is really no point to get a 4.0 x4 NVMe drive.

Asus B450 and X470 Motherboards That Support PCIe 4.0 (Updated)

Asus has listed all of the its B450 and X470 motherboards that partially support the latest PCIe 4.0 standard.

www.tomshardware.com

Edit: The idea is if I buy this 4.0x4 drive will I get the full PCIe 4.0x4 Speeds?

KC3000 PCIe 4.0 NVMe M.2 SSD High-performance for desktop and laptop PCs - Kingston Technology

KC3000 PCIe 4.0 NVMe M.2 SSD delivers next-level performance using the latest Gen 4x4 NVMe controller and 3D TLC NAND. It delivers outstanding endurance and improves the workflow in high-performance desktop and laptop PCs, making it ideal for power users who demand the fastest speeds on the market.

www.kingston.com

512GB – 7,000/3,900MB/s

 

[Dr. Dro]

I already have PCI-e 3.0x4 NVMe two WD SN570s. The main reason I never went with a 4.0x4 drive is because I thought I was limited to PCIe 3.0.

There are several articles online that shows the B450 can support 4.0 speeds and I don't mean that it backwards compatible. I mean performs like a 4.0 x4 NVMe should.

If its going to drop to 3.0 x4 then there is really no point to get a 4.0 x4 NVMe drive.

Asus B450 and X470 Motherboards That Support PCIe 4.0 (Updated)

Asus has listed all of the its B450 and X470 motherboards that partially support the latest PCIe 4.0 standard.

www.tomshardware.com

Edit: The idea is if I buy this 4.0x4 drive will I get the full PCIe 4.0x4 Speeds?

KC3000 PCIe 4.0 NVMe M.2 SSD High-performance for desktop and laptop PCs - Kingston Technology

KC3000 PCIe 4.0 NVMe M.2 SSD delivers next-level performance using the latest Gen 4x4 NVMe controller and 3D TLC NAND. It delivers outstanding endurance and improves the workflow in high-performance desktop and laptop PCs, making it ideal for power users who demand the fastest speeds on the market.

www.kingston.com

512GB – 7,000/3,900MB/s

It's blocked at the AGESA level. You won't benefit from 4.0 speeds on B450.

 

[AusWolf]

So I also noticed for some time that CPU-Z is showing PCI-e 4.0 support for my B450M Mortar Max
My current RX 480 only supports 3.0 x16.

Now If i wanted to get a PCie 4.0 x4 NVMe drive will the GPU cause a conflict with the Bus speeds?

No. Whatever device you have installed will run at the max supported speed by the motherboard and the device. They run their separate lanes, so there's no conflict. I haven't tried it on a B450, but I've built several other systems like that. My current rig has a PCI-e 3.0 GPU and 4.0 SSD and I'll have it the other way around after the upgrade I'm planning.

 

[The King]

Update on this some ASUS B450 definitely can run PCI-e 4.0x4 speeds. Still investigating if my MSi B450 can do the same but looking more like a pipe dream at this point.

 

[damric]

I had one of the gigabyte x370 boards with the beta BIOS for PCIE 4.0 but I never tried it. AMD should really unlock this now like they did with finally allowing the 5000 series on the oldest AM4 chipsets.