Is there any restriction on other components due to a PCIe 3.0 CPU?
Is there any restriction on other components due to a PCIe 3.0 CPU?
Hello... I've been thinking about this for a long time. If someone gets a PC with a CPU that's PCIe 3.0 locked, will it affect other components like a PCIe 4.0 motherboard, M.2 slot, and GPU? And if the motherboard supports PCIe 4.0 features such as Gen4 M.2 and a PCIe 4.0 GPU, will it still be restricted to PCIe 3.0 due to the CPU?
Yes, the CPU lacks the PCIe 4.0 lanes for these AMD Ryzen 5 4600G models. The chipset might allocate some lanes for additional M.2 slots, but it will remain at PCIe 3.0. Are you thinking about using this PC for yourself, a friend, or a client? Edited April 23, 2024 by filpo
It should utilize the CPU's PCIe lanes for the quickest data transfer between M.2 drives and expansion slots. If the CPU supports 3.0 lanes, that's the maximum bandwidth available. Compatibility with any PCIe device should work well, though performance might be slightly reduced. New lanes can't be added via a BIOS update—they're built into the CPU's hardware.
You can't take advantage of the maximum speed from Gen 4 SSDs and newer GPUs are also Gen 4. So I figured it's fine for gaming.
The sample PC only seems flawed unless it comes from a GPU upgrade. Otherwise, it will stick to PCIe3 because of the CPU. This won’t really matter unless you have a 4-lane GPU such as a 6400X, in which case your M2 performance will be limited to 3GB per second, though that’s not a major issue.
These components are distinct from the 4600G and APU dies, as they use a single integrated die rather than a modular MCM setup. Their performance typically matches that of a standard Zen3 8c/16t CPU running at the same frequency, though overall gains aren't identical. The monolithic designs feature only 16MB of L3 cache, much less than the 32MB found in Ryzen MCM configurations for Zen2 and later. Even the latest 8700G model shares this limitation. The North Bridge, responsible for I/O operations, has also seen improvements in the 8000G lineup to PCIe 4.0, though this applies only to AM5-based systems. A significant upgrade would boost PCIe speeds and better support the RX 6650 XT, especially if the system is close to a Microcenter. Just confirm your BIOS supports these changes before making any CPU adjustments.
I think you're overlooking the key idea here. Those PCIe 4 ports are physically connected straight to the CPU, making it the quickest link. The alternative would be using a CPU with a PCIe 4 port, but instead of wiring it directly, they added a PCIe 4 switch. If a GPU used PCIe 4 x8, it would gain the full speed of PCIe 3 x16 because the switch converts it. However, this setup wouldn<|pad|> to likely only support PCIe 3 x16, not the newer version. It would also increase cost, complexity, and introduce extra delay. In most scenarios, this approach wouldn't be better.
Computer parts operate based on the slowest component in their path. When a CPU uses PCIe Gen3 but the motherboard and GPU are Gen4, performance will be limited to Gen3 speeds since the CPU can't exceed that. Each new PCIe version doubles the data capacity per lane, offering strong backward compatibility. This limitation is most noticeable with PCIe Gen4 x8 cards, which match the bandwidth of a Gen3 x16 card. Pairing them with a Gen3 CPU results in only half the expected speed due to the reduced number of lanes.