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Ryzen 3000 series CPU PCIe lanes show 2.0 speeds (Asus ROG Strix B450-I Gaming)


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I'm pretty sure this has been a long standing issue, not one introduced by a recent update.

I don't know whether the on-package I/O die's PCIe capabilities are hardcoded or have to be detected for 400-series chipset boards (PCIe 3.0) vs 500-series chipset boards (PCIe 4.0), but at least on my ASUS ROG STRIX B450-I motherboard, the lanes are reported back as being PCIe 2.0 despite the fact that they're configured to 3.0 in BIOS and that I've observed that they're not actually running at 2.0 speeds.

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SSD bandwidth reads at greater than the 2GB/s they'd be capped to if the drives were actually running at 2.0 speeds, and GPU PCIe bandwidth comes in at higher than the 4GB/s that it would be capped to were it running at 2.0 speeds.

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As is often the case when I point out irregularities on an ASUS board, if the issue is down to their WMI interface, just let me know and I'll just ignore the incorrect values.

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12 hours ago, MrCommunistGen said:

I'm pretty sure this has been a long standing issue, not one introduced by a recent update.

I don't know whether the on-package I/O die's PCIe capabilities are hardcoded or have to be detected for 400-series chipset boards (PCIe 3.0) vs 500-series chipset boards (PCIe 4.0), but at least on my ASUS ROG STRIX B450-I motherboard, the lanes are reported back as being PCIe 2.0 despite the fact that they're configured to 3.0 in BIOS and that I've observed that they're not actually running at 2.0 speeds.

SSD bandwidth reads at greater than the 2GB/s they'd be capped to if the drives were actually running at 2.0 speeds, and GPU PCIe bandwidth comes in at higher than the 4GB/s that it would be capped to were it running at 2.0 speeds.

As is often the case when I point out irregularities on an ASUS board, if the issue is down to their WMI interface, just let me know and I'll just ignore the incorrect values.

PCI devices and their registers, including PCIe root port descriptors are configured by the BIOS at system bootup.  Apparently on your system the motherboard fails to put the right PCIe speed information into the PCI devices.  It's a minor cosmetical issue that you can freely ignore, especially that as you've proven using our benchmarks, the devices are indeed working in 3.0 mode.

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I was wondering about that on AMD/AM4 machines for some time too. But while being cosmetical, it would help a lot to quickly identify at what speed components are connected at without doing benchmarking or the need to use other tools just for that purpose. Not only for NVMe SSDs, but also things like secondary graphics cards and 10Gbit network cards are dependend on fast interconnection. Putting it into the wrong slot may cause halfing or even quatering of the bandwitdth.

 

I've experienced this on any AM4 system I have used so far:

ASUS ROG STRIX B350-F GAMING // Ryzen 1600

ASUS PRIME B450M-A // Ryzen 1800X

ASUS PRIME X470-PRO // Ryzen 2600X

GIGABYTE B550 AORUS PRO // Ryzen 3600 & Ryzen 5600

 

Being the same on any Ryzen generation, AM4 chipset and two makers of mainboards, it can only be a (cosmetical) serial fault that still persists, or AIDA64 misinterpreting something. If it is the former, I suspect other tool makers reading out the same PCIe 2.0 values, but transforming them into the expected values guessed from the present CPU and MB combination. :rolleyes:

Judging by your words, dear Fiery, "Apparently on your system the motherboard fails..." you suggest that you either know it should work, or you havn't had the opportunity yet. What could it be? :unsure:

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On 1/6/2021 at 12:46 AM, WilleHelm said:

I was wondering about that on AMD/AM4 machines for some time too. But while being cosmetical, it would help a lot to quickly identify at what speed components are connected at without doing benchmarking or the need to use other tools just for that purpose. Not only for NVMe SSDs, but also things like secondary graphics cards and 10Gbit network cards are dependend on fast interconnection. Putting it into the wrong slot may cause halfing or even quatering of the bandwitdth.

 

I've experienced this on any AM4 system I have used so far:

ASUS ROG STRIX B350-F GAMING // Ryzen 1600

ASUS PRIME B450M-A // Ryzen 1800X

ASUS PRIME X470-PRO // Ryzen 2600X

GIGABYTE B550 AORUS PRO // Ryzen 3600 & Ryzen 5600

 

Being the same on any Ryzen generation, AM4 chipset and two makers of mainboards, it can only be a (cosmetical) serial fault that still persists, or AIDA64 misinterpreting something. If it is the former, I suspect other tool makers reading out the same PCIe 2.0 values, but transforming them into the expected values guessed from the present CPU and MB combination. :rolleyes:

Judging by your words, dear Fiery, "Apparently on your system the motherboard fails..." you suggest that you either know it should work, or you havn't had the opportunity yet. What could it be? :unsure:

All I know is that in theory the BIOS should clearly know what to put into the mentioned PCI registers to make sure everything looks okay and accurate about the PCI Express Root Ports, both their capabilities and their current/active settings.  The reason why it's not the case on many motherboards must be negligence on the part of the BIOS engineers.  If you have doubts about whether it's a BIOS bug or an AIDA64 bug, just check the reported information against information reported by another sysinfo software.

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