Search Keywords : "Memory Limits for Windows"
https://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx
[ x64 = 64bit ]
Windows 10 Enterprise : 2 TB.
Windows 10 Education : 2 TB.
Windows 10 Pro : 2 TB.
Windows 10 Home : 128 GB.
Windows 8.1 Professional : 512 GB.
Windows 8 Enterprise : 512 GB.
Windows 8 Professional : 512 GB / 2 CPUs.
Windows 8 : 128 GB.
Windows 7 Ultimate : 192 GB / 2 CPUs.
Windows 7 Enterprise : 192 GB.
Windows 7 Professional : 192 GB / 2 CPUs.
Windows 7 Home Premium : 16 GB.
Windows 7 Home Basic : 8 GB.
Windows Embedded Standard 7 : 192 GB.
Windows XP Professional : 128 GB.
Windows Server 2012 R2 Datacenter : 4 TB / 64 CPUs. (2CPU Per LIC)
Windows Server 2012 R2 Standard : 4 TB / 64 CPUs. (2CPU/2VMs Per LIC)
Windows Server 2012 R2 Essentials : 64 GB / 2 CPUs.
Windows Server 2012 R2 Foundation : 32 GB / 1 CPU.
Windows Server 2012 Datacenter : 4 TB / 64 CPUs. (2CPU Per LIC)
Windows Server 2012 Standard : 4 TB / 64 CPUs. (2CPU/2VMs Per LIC)
Windows Server 2012 Essentials : 64 GB / 2 CPUs.
Windows Server 2012 Foundation : 32 GB / 1 CPU.
Windows Storage Server 2012 Workgroup : 32 GB.
Windows Storage Server 2012 Standard : 4 TB.
Hyper-V Server 2012 : 4 TB.
Windows Server 2008 R2 Datacenter : 2 TB.
Windows Server 2008 R2 Enterprise : 2 TB / 8 CPUs.
Windows Server 2008 R2 Standard : 32 GB / 4 CPUs.
Windows Server 2008 R2 Foundation : 8 GB / 1 CPU.
Windows Storage Server 2008 R2 Standard : 32 GB / 4 CPUs.
Windows HPC Server 2008 R2 : 128 GB.
Windows Web Server 2008 R2 : 32 GB.
Windows Server 2008 Datacenter : 1 TB.
Windows Server 2008 Enterprise : 1 TB.
Windows Server 2008 HPC Edition : 128 GB.
Windows Server 2008 Standard : 32 GB.
Windows Small Business Server 2008 : 32 GB.
Windows Web Server 2008 : 32 GB.
Windows Server 2003 R2 Datacenter : 1 TB.
Windows Server 2003 R2 Enterprise : 1 TB.
Windows Server 2003 R2 Standard : 32 GB.
[ x86 = 32bit ]
Windows 10 Pro : 4 GB.
Windows 8 Professional : 4 GB / 2 CPUs.
Windows 7 Ultimate : 4 GB.
Windows 7 Enterprise : 4 GB.
Windows 7 Professional : 4 GB / 2 CPUs.
Windows 7 Home Premium : 4 GB.
Windows 7 Home Basic : 4 GB.
Windows 7 Starter : 2 GB.
Windows XP Professional : 4 GB.
Windows XP Starter : 512 MB.
Windows XP Embedded : 4 GB.
Windows Embedded Standard 2009 : 4 GB.
Windows Server 2008 Datacenter : 64 GB.
Windows Server 2008 Enterprise : 64 GB.
Windows Server 2008 Standard : 4 GB.
Windows Small Business Server 2008 : 4 GB.
Windows Web Server 2008 : 4 GB
Windows Server 2003 R2 Datacenter : 64 GB. (16 GB with 4GT)
Windows Server 2003 R2 Enterprise : 64 GB. (16 GB with 4GT)
Windows Server 2003 R2 Standard : 4 GB.
Windows Server 2003 Datacenter with SP2 : 64 GB. (16 GB with 4GT)
Windows Server 2003 Enterprise with SP2 : 64 GB. (16 GB with 4GT)
Windows Server 2003 Standard with SP2 : 4 GB.
Windows Server 2003 Datacenter : 64 GB. (16 GB with 4GT)
Windows Server 2003 Enterprise : 64 GB. (16 GB with 4GT)
Windows Server 2003 Standard : 4 GB.
Windows Server 2003 Web Edition : 2 GB.
Windows Small Business Server 2003 : 4 GB.
Windows Storage Server 2003 Enterprise : 8 GB.
Windows Storage Server 2003 : 4 GB.
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