en.wikipedia.org/wiki/X86-64
2 corrections found
The AMD64 architecture defines a 64-bit virtual address format, of which the low-order 48 bits are used in current implementations.
Current AMD64 implementations are no longer limited to 48-bit virtual addresses. AMD documentation for EPYC 9004 shows 57-bit virtual addressing.
Full reasoning
This statement is outdated. AMD’s own documentation for current EPYC 9004 processors shows 57 bits virtual address size, not 48 bits.
AMD’s 4th Gen EPYC architecture material also states that virtual memory is now addressable through 57 bits with a fifth level of page tables. So it is no longer correct to say that current AMD64 implementations use only the low-order 48 bits of the virtual address.
2 sources
- Red Hat Enterprise Linux Tuning Guide for AMD EPYC 9004 Series Processors
Architecture: x86_64 ... Address sizes: 52 bits physical, 57 bits virtual ... Model name: AMD EPYC 9654 96-Core Processor.
- 4th Gen AMD EPYC Processor Architecture
With the potential to expand memory through CXL controllers, virtual memory is now addressable through 57 bits, and a fifth level of nested page tables has been implemented to support this.
Current implementations of the AMD64 architecture (starting from AMD 10h microarchitecture) extend this to 48-bit physical addresses
Current AMD64 implementations are not limited to 48-bit physical addresses. AMD documents current EPYC 9004 processors as using 52-bit physical addressing.
Full reasoning
AMD documentation for current EPYC 9004 processors reports 52 bits physical address size, not 48 bits.
AMD’s March 2026 AMD64 Architecture Programmer’s Manual, Volume 2: System Programming likewise says the architecture’s page-translation mechanism supports translation of a 64-bit virtual address to a 52-bit physical address. That means the article’s claim that current implementations extend only to 48-bit physical addresses is outdated/incorrect.
2 sources
- Red Hat Enterprise Linux Tuning Guide for AMD EPYC 9004 Series Processors
Architecture: x86_64 ... Address sizes: 52 bits physical, 57 bits virtual ... Model name: AMD EPYC 9654 96-Core Processor.
- AMD64 Architecture Programmer’s Manual, Volume 2: System Programming
The AMD64 architecture defines an expanded page-translation mechanism supporting translation of a 64-bit virtual address to a 52-bit physical address.