Intel Alder Lake, new information on PCI Express configurations

Intel Alder Lake, new information on PCI Express configurations
Alder Lake will not only be the first processor to bring an x86 hybrid architecture to desktops, but CPUs will also be able to take advantage of the all-new PCI Express 5.0 interface. Coreboot (as spotted by well-known leaker @Komachi_Ensaka), an open source replacement for UEFI, appears to contain invaluable information on potential PCIe configurations that we will be able to see on Alder Lake.

Early rumors stated that 12th-grade Alder Lake processors generation would support both PCIe 5.0 and PCIe 4.0 standards and Tim Wawrzynczak's code analysis seems to confirm this. However, the code refers specifically to Alder Lake-P (ADL-P), so it's not sure if the same will also apply to the Alder Lake-S variant. We still have no idea what Alder Lake-P will be, but some think it could be Intel's Atom P series or a mobile chip. However, a previous coreboot patch revealed that Alder Lake-P could reach a maximum of 14 cores, split between six Golden Cove and eight Gracemont.

Alder Lake-P appears to provide a flexible PCIe layout. The processor reportedly offers one PCIe 5.0 x8 or two PCIe 4.0 x4 connection. Unfortunately, neither interface should support bifurcation, which means it is not possible to split the PCIe 5.0 connection or run those PCIe 4.0 at x8. However, both are backwards compatible with previous generation devices.

Interface x16 x8 x4 x2 x1 PCIe 5.0 64 GBps 32 GBps 16 GBps 8 GBps 4 GBps PCIe 4.0 32 GBps 16 GBps 8 GBps 4 GBps 2 GBps PCIe 3.0 16 GBps 8 GBps 4 GBps 2 GBps 1 GBps PCIe 2.0 8 GBps 4 GBps 2 GBps 1 GBps 0.5 GBps PCIe 1.0 4 GBps 2 GBps 1 GBps 0.5 GBps 0.25 GBps The presence of a single PCIe 5.0 x8 connector might seem rather disappointing, but it actually offers a lot of bandwidth. PCIe 5.0 x8 is essentially equivalent to PCIe 4.0 x16, so the interface is capable of delivering 32GB / s of bandwidth. Until now, only AMD's Ryzen 3000 and Ryzen 5000 mainstream processors have embraced PCIe 4.0, but that is expected to change soon with the introduction of Intel's Rocket Lake series.

There are some PCIe products Traditional 4.0, including graphics cards and M.2 SSDs, on the market right now. Tests have shown that even the fastest GPUs are unable to saturate a PCIe 3.0 x16 interface and even less a PCIe 4.0. M.2 SSDs, on the other hand, were able to take advantage of the additional bandwidth that PCIe 4.0 made available.

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