Talk:POWER9 Hardware Compatibility List/PCIe Devices

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What is the impact of incomplete PCIe address space (eg. 40 instead of 64 bits)?

This page says:

> Incomplete memory addressing support. The PCIe architecture specifies a 64-bit address space. > Some I/O devices try to economize on this by only implementing e.g. 40 bits for their addressing, > rendering them incapable of addressing host memory which lies above address 240. (Firmware patches to work around this are pending.)

2^40 means 1 TB of RAM. Does this mean I can still use this these PCIe devices without any unwanted side-effects if I do not have more than 128 GB RAM?


JMicron JMB585 EEH on Linux 7.x

From what I understand, a bug was found in the JMB585 firmware/hardware that causes silent corruption (detectable on btrfs or zfs) under heavy load. The fix is forcing the kernel to treat these cards at 32bit PCI devices, and you'll see "controller can't do 64bit DMA, forcing 32bit" in dmesg. I don't think there's a workaround for users. Bobpaul (talk) 17:24, 31 July 2026 (CDT)

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