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Why would BIOS count 3 GB and Vista show 4 GB RAM?

Why would BIOS count 3 GB and Vista show 4 GB RAM?

I upgraded my Vista computer from 2GB to 4GB of RAM.

Asked by: Guest | Views: 243
Total answers/comments: 3
Guest [Entry]

"The reason that Windows reports 4GB of RAM is because Vista is lying to you.

Remember that when Vista was released, purchasing 4GB of RAM was becoming much more cost-effective for the average user. Saying that the OS only reported 3GB of RAM when you knew your machine had 4 GB installed probably caused all kinds of support calls and support costs for Microsoft. The cheapest and simplest solution was to just change what Vista reported to the user, regardless of how much memory was addressable. My guess is that any amount of RAM greater than or equal to 3GB triggers x86 Vista reporting 4GB installed.

Vista SP1 Notable Changes

With SP1, Windows Vista will report
the amount of system memory installed
rather than report the amount of
system memory available to the OS.
Therefore 32-bit systems equipped with
4GB of RAM will report all 4GB in many
places throughout the OS, such as the
System Control Panel. However, this
behavior is dependent on having a
compatible BIOS, so not all users may
notice this change."
Guest [Entry]

Best explained by Jeff - Where's my RAM ?
Guest [Entry]

"The reason for the discrepancy is as mentioned above how Vista reports memory size.

The solution however when running a 64-bit OS is to enable a BIOS feature called memory remap. This is by default disabled in the BIOS because it breaks compatibility with 32-bit OS:s.

What the feature does is that instead of mapping your gfx card/io cards and such below the 4GB boundry it moves everything above the 4GB boundry. The result is that it does not steal the address space and you can therefore use all 4GB of memory. It will also report the correct size at the BIOS screen."