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 processors
64-bit long mode
32-bit legacy mode
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
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
• 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.
From the document titled "AMD64 Architecture Programmer's Manual, Vol. 1: Application Programming,"
Yes – to OS
No – to application