What exactly does “Memory Remapping“ mean?
Memory Remapping is also known as the “4GB problem” and frustrates many PC users. Whoever attempts to install more than 3GB into their system will notice that despite correctly installing the devices, both the system and the BIOS will report that only a capacity of 3.25GB is available.
How does this come about?
Not only PCI and AGP-cards, but also the IDE-bus are only capable of operating at a 32-bit level. This means that only 32-bit addresses can be recognised by these components. The BIOS on a motherboard reserves a not insignificant amount of addresses (i.e. memory) for these input & output devices. The amount of memory reserved is usually somewhere between 3 and 4GB, but never exceeds the 32-Bit limitation.
The lion’s share of the memory that the BIOS reserves is taken by the graphics card. Up until a few years ago, the address range was larger than the amount of memory being used. For example, 512MB were considered sufficient at that point in time. Today, computer users will exceed those numbers by a margin that 32-Bit systems were not designed to handle.
Unlocking the full potential of your memory with Memory Remapping
Memory Remapping allows for the installed but previously unusable memory to be utilised to its full potential. It renders the previously “invisible” memory, beyond the 4GB limitation, visible.
Memory Remapping isn’t much use to 32-Bit systems; however, as the system limitation of 32-Bits ultimately corresponds to 4GB. Windows XP, for example, will continue to use 3,25GB, even after Memory Remapping. Windows Vista behaves the same way: after initialising Memory Remapping, the system will display 4GB of usable memory but only uses 3,25GB. This is due to a restriction put in place by Microsoft. It is only possible to make full use of the 4GB by activating an additional extension (PAE – Physical Address Extension) and using a 32-Bit server variant.
But there are exceptions to this process, Windows Server 2003 Web-Edition, for example, is hard locked to a maximum of 2GB of memory.
Conversely, 64-Bit Systems can operate much more efficiently as Memory Remapping is activated as standard.
Windows 7 users with a 64-bit system will find more information and advice in our “Troubleshooting Quick guide” if your RAM upgrade didn’t lead to the desired result.