HP ML115 The AMD processor roadmap for industry-standard servers, 6th edition - Page 4

Operating modes AMD Opteron processors use three different operating modes: 64-bit long mode, 64-bit compatibility mode, and 32-bit legacy mode. The 64-bit long mode requires a 64-bit OS and an application recompiled to use the 64-bit registers. In other words, the full capabilities of the expanded register set are available only when both the OS and the application support 64 bits. The 64-bit compatibility mode requires a 64-bit OS, but can use a 32-bit application. The additional registers are available to the OS, but not to the 32-bit application, because it cannot make use of them. When running in legacy mode, the processor acts just like a 32-bit processor, and the extra registers are not available (Table 2). Table 2. Operating modes for AMD Opteron processors2 Mode 64-bit long mode 64-bit compatibility mode OS required 64-bit OS 64-bit OS Application recompile required? Yes No 32-bit legacy mode 32-bit OS No Register extensions available? Yes Yes - to OS No - to application No GPR width (bits) 64 32 32 Memory addressability The AMD Opteron registers are at least 64-bits wide. When operating in 64-bit long mode, the AMD Opteron processors support up to 48 bits (256 Terabytes) for physical memory and use 64 bits for virtual memory Naming conventions First-generation single-core AMD Opteron processors (Socket 940 and Socket 939) have three-digit model numbers in the form XZZ, and third-generation Quad-Core AMD Opteron processors (Socket F and Socket AM2) have four-digit model numbers XYZZ. AMD Opteron processor "generations" are called Revisions. For all AMD Opteron processors, the first digit "X" specifies the number of CPUs on the target machine: • 1000 Series - Single-processor systems • 2000 Series - Dual-processor systems • 8000 Series - Systems with up to 8 processors The second digit, Y, indicates socket generation, where "2" indicates Socket AM2 or Socket F (1207). Series 12ZZ processors are based on Socket AM2; Series 22ZZ and 82ZZ processors are based on Socket F (1207). If the second digit is "3," it stands for third-generation AMD Opteron processors for Socket AM2 and Socket F (1207). If the second digit is "4," it indicates Six-Core AMD Opteron processors. 2 From the document titled "AMD64 Architecture Programmer's Manual, Vol. 1: Application Programming," available at www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/24592.pdf 4