14 DAY TRIAL // Microsoft's latest operating system comes in both 32-bit and 64-bit flavors, but all the editions of Windows Vista have problems using a full 4 GB of RAM. Unlike Apple, which controls the entire hardware and software ecosystem, Microsoft doesn't have the luxury of scraping support for 32-bit platforms. This is why Vista brings to the table 32-bit and 64-bit editions, an aspect that will remain valid even for its successor, Windows 7 (Seven), currently planned for 2010. One of the main benefits of x64 operating systems, including Vista, is the fact that the platforms support well in excess of 4 GB of system memory. Generally speaking, 32-bit Windows Vista are limited to addressing 3,120 megabytes (MB) of random-access memory.
This means that even if you have a full 4 GB of RAM installed on your machine, a 32-bit copy of Vista will only reveal 3.12 GB. The limitation is associated with a cocktail of hardware and software factors. X64 Windows Vista is designed to not be affected by such behavior. As a matter of fact, high end editions of Windows Vista (Business, Enterprise and Ultimate) can address a total of 128 GB of RAM. Still, it is important to understand that 64-bit Vista alone is by no means sufficient to address 4 GB of RAM. In this context, it is not the fault of the operating system, but that of the hardware.
Simply put, you need to support a copy of 64-bit Windows Vista with a certain hardware configuration in order for the operating system to address and use all the 4 GB of RAM installed. In this regard, x64 Vista is intimately connected with the chipset, the CPU and the BIOS. Microsoft offers the hardware configuration necessary for x64 Vista to address a full 4 GB of RAM:
￭ The chipset must support at least 8 GB of address space. Chipsets that have this capability include the following: Intel 975X, Intel P965, Intel 955X on Socket 775; chipsets that support AMD processors that use socket F, socket 940, socket 939, or socket AM2. These chipsets include any AMD socket and CPU combination in which the memory controller resides in the CPU. ￭ The CPU must support the x64 instruction set. The AMD64 CPU and the Intel EM64T CPU support this instruction set. ￭ The BIOS must support the memory remapping feature. The memory remapping feature allows for the segment of system memory that was previously overwritten by the Peripheral Component Interconnect (PCI) configuration space to be remapped above the 4 GB address line. This feature must be enabled in the BIOS configuration utility on the computer. View your computer product documentation for instructions that explain how to enable this feature. Many consumer-oriented computers may not support the memory remapping feature.