AM5 PCIe speed limitation
AM5 PCIe speed limitation
Exploring the performance of using all m.2, sata and PCIe ports on the X670E. Assessing how the motherboard and the 4.0x4 downlink CPU manage this setup.
Unless you're relying heavily on multiple drives connected via the chipset simultaneously, you probably won't face bandwidth challenges. SATA drives reach up to 600MB/s, far below the ~7GB/s capacity of the link through the chipset. Even with numerous PCIe devices in use, unless you're moving large files between drives, the controller will remain the limiting factor before the PCIe connection reaches the CPU. In reality, for most scenarios, pushing your PCIe and input connections to their limits won't lead to noticeable issues.
PCIE is quicker than anything else, no need to fear losing performance. The term bottleneck should be removed.
As long as you're not transferring big files at once, it should go unnoticed. A PCIe 5.0/4.0 M.2 drive operating at four times speed might still function at one time without you realizing it, unless you're in that situation. Checking the motherboard's schematic in the manual before buying helps avoid issues, particularly if you plan to fill all available slots. Some boards have SATA ports shared with M.2 or PCIe connections, which can cause conflicts.
The setup you're describing involves connecting multiple 4.0x4 chipsets in a chain, with the USB port at the end. This configuration can work well as long as each chipset is properly managed and the total bandwidth demand stays within limits. Since the USB device is the final one in the chain, it won't be affected by upstream drives. If you're using Gen4 drives, they should handle higher speeds without straining the system. Just ensure the chipsets are correctly configured and monitored for performance.
No way, it doesn’t get that much usage in everyday situations.
Are you planning to use several drives at once for big file moves? I mean files that are bigger than 1GB each—not the number of files being sent. This is important because NVMe speeds only really hit their limit in real situations like this one. Moving games, code, Blender projects, or everyday files most people handle usually means sending many tiny files. These small files will get stuck before reaching the PCIe connection, which is why actual transfer speeds are much lower than advertised. In practice, you’re often moving a mix of small, medium, and large files in one go. The tiny ones slow things down due to file system and drive controller limits. A system backup is a typical case—most files are small, PCIe stays fast, and traffic over it remains light unless you’re dealing with huge video or archive files.
PCIe speed is typically increased beyond what’s needed for most tasks. This is why a high-end RTX 4090 using PCIe 1.1 x16 can still surpass other cards at 4K resolution. The less data sent directly to the CPU, the less impact it has. When compared to storage devices, unless you’re repeatedly copying or saving huge files to fill the bus, you probably aren’t utilizing much of it. Generally, the South Bridge has consistently delivered this role. In such cases, an HBA or a PCIe SATA controller working independently from the North Bridge PCIe path is preferable. The North Bridge is meant for critical PCIe components, even back then when it was integrated onto the motherboard rather than on the CPU chip (like Ryzen’s I/O die or Intel’s ‘uncore’). The South Bridge is reserved for secondary PCIe peripherals. Even Intel’s 4.0 8x south bridge interconnect is unlikely to cause issues under similar conditions.
I refer to files such as zip and video formats that range from a few gigabytes up to 150 gigabytes.
In that scenario, the chipset could become a limitation when moving files across several drives at once. However, even with a doubled connection, you still receive 3.5GB/s at PCIe 4.0 speeds. If your data rate drops, a 150GB file will finish in 43 seconds instead of 22. Keep in mind this speed drop only occurs during simultaneous transfers; otherwise, you'll maintain full performance for single files. This isn't a major performance hit in practical terms. I recognize the value of time, but if waiting 20 seconds for a transfer seriously affects your work, it's worth switching to professional hardware like HEDT or server systems with many PCIe lanes connected directly to the CPU. Although more expensive, this upgrade is justified when time is critical.