When buying a new PC, should you spend the extra cash to upgrade your RAM? Here’s a rule-of-thumb for how much memory you need to run Windows Vista:
Windows Vista RAM
- 2 GB is minimum
- 3 GB if you can afford it
- 4 GB is mostly wasted (on 32-bit Vista)
If a PC has 4 gigabytes (GB) of random-access memory (RAM) installed, Windows Vista will show significantly less than 4 GB available memory. For example, the Vista “System Information” dialog box may report 3,120 megabytes (MB) of memory available on a PC that has 4,096 MB (4 GB) of memory installed. Note this only applies to the 32-bit versions of Vista; the 64-bit versions of Vista can access up to 128 GB of RAM.
To see how much memory you have available in Windows Vista:
- Double-click System in Control Panel, -or-
- Click Start, right-click Computer, and then click Properties
The missing RAM on a 4 GB system is “stolen” by various devices that require memory-mapped I/O (MMIO). Since a 32-bit operating system can only access 4 GB of address space, these devices are granted space starting from the 4 GB address and working backward. Devices include:
- BIOS, ACPI and legacy video support
- PCI bus for hard disks, sound cards, LAN cards, etc.
- PCI Express can consume 256-768 MB for the graphics card
So if a PC has 4 GB RAM installed, some of that 4 GB is used for MMIO. The amount of missing RAM depends on the devices installed in the PC. But because of driver compatibility issues, the 32-bit versions of Vista limit available memory to 3.12 GB.
- The 3GB-not-4GB RAM problem
- Microsoft: Memory reported in Vista is less than you expect if 4 GB of RAM is installed
Article published on February 9, 2008
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