BIOS Feature Requirements of AMD GPUs

Question

What are the requirements of AMD GPUs for BIOS features?

Answer

AMD GPUs have varying DMA addressing bit widths, primarily 40-bit and 44-bit. See the following table for details. The addressing bit width determines the maximum addressable range for DMA target addresses allocated by the system kernel to a GPU. On the Kunpeng 920 server, the physical memory addresses associated with CPU 2 (the second CPU on the mainboard) reside in a space above 32 TB (46-bit), which exceeds the maximum addressing space of AMD GPUs. This limitation causes some AMD GPUs to use memory on CPU 1 only. In a cloud phone scenario, half of the containers use CPU 2 and its local memory, and this part of memory cannot interact with the GPUs. Therefore, you can restrict the memory address range of CPU 2 via BIOS settings to ensure that the GPUs can interact with all memory.

**Table 1** Mapping between AMD GPUs and BIOS features (40Bit or 44Bit)
GPU Model	Device ID	BIOS 40Bit or 44Bit
AMD Radeon Pro WX 5100	0x67c7	40
AMD Radeon Pro W5500	0x7341	44
AMD Radeon Pro W6600	0x73e3	44
AMD Radeon Pro W6800	0x73a3	44

**Table 2** Comparison between BIOS 40Bit and 44Bit features of Kunpeng servers
BIOS Feature	Earliest BIOS Version	Description
40Bit	V163 (v1.63)	When enabling the 40Bit feature (setting Support 40Bit to Enabled), note that: The recommended DIMM insertion method is used, and socket interleaving cannot be used. The memory size of a single CPU cannot exceed 256 GB. This feature cannot be used together with the PoE feature. Ensure that SMMU is disabled.
44Bit	V177 (v1.77)	When enabling the 44Bit feature (setting Support 44Bit to Enabled), note that: The recommended DIMM insertion method is used, and socket interleaving cannot be used. This feature cannot be used together with the PoE feature. Ensure that SMMU is disabled. When both Support 40Bit and Support 44Bit are Enabled, only Support 40Bit takes effect.