Table of Contents
Advertisement
act just like any other IA32-compatible processor. You can install your
32-bit operating system on such a system and run 32-bit applications, but
you cannot use the new features such as the flat memory addressing
above 4 GB or the additional GPRs. Thirty-two-bit applications run as fast
as they would on any current 32-bit processor.
Most of the time, IA32 applications run even faster because numerous
other improvements boost performance regardless of the maximum
address size.
– Compatibility mode
The
which we describe next. To run in compatibility mode, you have to install a
64-bit operating system and 64-bit drivers. When a 64-bit OS and drivers
are installed, the processor can support both 32-bit applications and 64-bit
applications.
The compatibility mode provides the ability to run a 64-bit operating
system while still being able to run unmodified 32-bit applications. Each
32-bit application still is limited to a maximum of 4 GB of physical memory.
However, the 4 GB limit is now imposed on a per-process level, not on a
system-wide level. This means that every 32-bit process on this system
gets its very own 4 GB of physical memory space, provided sufficient
physical memory is installed. This is already a huge improvement
compared to IA32, where the operating system kernel and the application
had to share 4 GB of physical memory.
Because the compatibility mode does not support the virtual 8086 mode,
real-mode applications are not supported. However, sixteen-bit protected
mode applications are supported.
– Full 64-bit mode
The
AMD™, it is the
64-bit application are used. In the full 64-bit operating mode, an
application can have a virtual address space of up to 40 bits, equating to
one terabyte (TB) of addressable memory. The amount of physical
memory is determined by how many DIMM slots the server has, and the
maximum DIMM capacity supported and available at the time.
Applications that run in full 64-bit mode have access to the full physical
memory range, depending on the operating system, and also have access
to the new GPRs as well as to the expanded GPRs. However, it is
important to understand that this mode of operation requires not only a
64-bit operating system (and, of course, 64-bit drivers) but also a 64-bit
application that has been recompiled to take full advantage of the various
enhancements of the 64-bit addressing architecture.
38
Planning, Installing, and Managing the IBM System x3950 M2
compatibility mode
is an intermediate mode of the full 64-bit mode,
full 64-bit mode
is referred to by Intel as the
long mode
.) This mode is applied when a 64-bit OS and
IA-32e mode
. (For
Advertisement
Table of Contents
