Windows 7 will take the maximum amount of supported system memory well beyond the limits of Windows Vista. In this regard, the high-end edition of the upcoming Windows client will play nice with just a tad short of 200 GB of Random Access Memory. At the same time, Windows 7 has been designed to work under normal parameters starting with as little as 1 GB of RAM, in order to fit onto cheap and resource-constrained netbooks. However, given proper hardware, namely if the mainboard can handle increased amounts of system memory, Windows 7 Ultimate is ready to swallow no less than 192 GB of RAM.
This is of course valid for 64-bit versions of the next iteration of Windows, running on top of x64 CPUs, according to WinSuperSite. As far as the 32-bit editions of Windows 7 are concerned, the limit continues to be 4 GB of RAM. However, even if Windows 7 correctly reports all 4 GB of RAM installed on a machine, the 32-bit versions of the platform will not be able to address all of it.
x86 architectures have a limited address space, just 4 GB in total, and they have to fit all hardware components, leaving at maximum just 3.5 GB, but more in the vicinity of 3.3 GB for RAM. As you can see in the screenshot accompanying this article, my 32-bit Windows 7 Build 7100 Ultimate is only able to address and use 3.37 GB of RAM out of the total 3.5 GB installed. This limitation is valid for all editions of Windows 7 32-bit.
But this is not the case for the 64-bit flavor of Windows 7. The Home Basic and Starter SKUs can manage up to 8 GB of RAM, with Home Premium taking the limit to 16 GB. The Professional, Enterprise and Ultimate versions of Windows 7 will support as much as 192 GB of RAM.
By comparison, while 32-bit editions of Vista were also limited to 4 GB, 64-bit SKUs could deal with more system memory. Home Basic could take 8 GB, Home Premium 16 GB, while Business, Enterprise and Ultimate would go as high as 128 GB.