Analysis of information sources in references of the Wikipedia article "3 GB barrier" in English language version.
In uni-processor based systems for mobile, desktop, workstation, and entry level servers, chipsets may be limited to 4 GB of maximum memory. In today's dual processor Intel server chipsets and workstations, maximum system memory size can be upwards of 16 GB.
In platforms populated with physical memory sizes approaching 4 GB and greater, onboard system resource requirements will likely not allow the operating system to take advantage of all physical memory populated due to PCI specification requirements and other memory mapped IO resources. Portions of physical memory may overlap with the memory space dedicated to other subsystems and become unavailable to the operating system.
In order to use remapping, the operating system must be able to address ranges higher than 4 GB of memory.
The Pentium Pro processor physical address space is 236 bytes or 64-Gigabytes (64 Gbyte).
Pin #: C1; Signal Name: A35#
Fedora 8 includes the following kernel builds: ... The kernel-PAE, for use in 32-bit x86 systems with more than 4GB of RAM, or with CPUs that have an NX (No eXecute) feature.
Devices have to map their memory below 4 GB for compatibility with non-PAE-aware Windows releases. Therefore, if the system has 4GB of RAM, some of it is either disabled or is remapped above 4GB by the BIOS. If the memory is remapped, X64 Windows can use this memory. X86 client versions of Windows don't support physical memory above the 4GB mark, so they can't access these remapped regions.
Windows Server 2008 Enterprise; Limit in 32-bit Windows: 64 GB
A 32-bit system is limited to utilizing 4GB of RAM (232 addresses)
Windows XP SP2 also enabled Physical Address Extensions (PAE) support by default on hardware that implements no-execute memory because its required for Data Execution Prevention (DEP), but that also enables support for more than 4GB of memory.
Windows XP SP2 also enabled Physical Address Extensions (PAE) support by default on hardware that implements no-execute memory because its required for Data Execution Prevention (DEP), but that also enables support for more than 4GB of memory. […] The problematic client driver ecosystem led to the decision for client SKUs to ignore physical memory that resides above 4GB, even though they can theoretically address it. […] 4GB is the licensed limit for 32-bit client SKUs.
Physical Address Extension is a technology which allows 32 bit operating systems to use up to 64 GB of memory... PAE is supported on the majority of computers today and it is an easy procedure to enable it in Ubuntu, if it is not already.
32-bit processors like Intel's Pentium III/IV and AMD's Athlon have a memory limit of 4 GB per CPU. Any more memory can't be addressed.
In uni-processor based systems for mobile, desktop, workstation, and entry level servers, chipsets may be limited to 4 GB of maximum memory. In today's dual processor Intel server chipsets and workstations, maximum system memory size can be upwards of 16 GB.
Windows XP SP2 also enabled Physical Address Extensions (PAE) support by default on hardware that implements no-execute memory because its required for Data Execution Prevention (DEP), but that also enables support for more than 4GB of memory.
In platforms populated with physical memory sizes approaching 4 GB and greater, onboard system resource requirements will likely not allow the operating system to take advantage of all physical memory populated due to PCI specification requirements and other memory mapped IO resources. Portions of physical memory may overlap with the memory space dedicated to other subsystems and become unavailable to the operating system.
In order to use remapping, the operating system must be able to address ranges higher than 4 GB of memory.
Windows XP SP2 also enabled Physical Address Extensions (PAE) support by default on hardware that implements no-execute memory because its required for Data Execution Prevention (DEP), but that also enables support for more than 4GB of memory. […] The problematic client driver ecosystem led to the decision for client SKUs to ignore physical memory that resides above 4GB, even though they can theoretically address it. […] 4GB is the licensed limit for 32-bit client SKUs.
32-bit processors like Intel's Pentium III/IV and AMD's Athlon have a memory limit of 4 GB per CPU. Any more memory can't be addressed.
