4gb RAM in vista, 3Gb in Xp

[simpatiko]

I bought a laptop with vista home premium almost two years ago. It had 2 Gb
of RAM. I upgraded it to 4GB of RAM and vista would show the 4GB in the
system properties box. Then I changed to Windows XP Professional and now the
system properties box shows only 2.99 GB of RAM. Why is this?

 

[Bennett Marco]

I bought a laptop with vista home premium almost two years ago. It had 2 Gb
of RAM. I upgraded it to 4GB of RAM and vista would show the 4GB in the
system properties box. Then I changed to Windows XP Professional and now the
system properties box shows only 2.99 GB of RAM. Why is this?

Was your version of Vista 64-bit?

 

[lemel_man]

I bought a laptop with vista home premium almost two years ago. It had 2 Gb
of RAM. I upgraded it to 4GB of RAM and vista would show the 4GB in the
system properties box. Then I changed to Windows XP Professional and now the
system properties box shows only 2.99 GB of RAM. Why is this?

In 32 bit mode you can only address 4GB. Period.
Even though your graphics card has its own memory it has to be mapped
into that 4GB address space, from the highest possible address
downwards. So, if the graphics card has 1GB memory, the last 1GB of your
actual 4GB RAM cannot be used.
The situation is different for 64-bit OSs, where the graphics card
memory can be mapped far away from the end of your 4GB.

 

[Ian D]

I bought a laptop with vista home premium almost two years ago. It had 2
Gb
of RAM. I upgraded it to 4GB of RAM and vista would show the 4GB in the
system properties box. Then I changed to Windows XP Professional and now
the
system properties box shows only 2.99 GB of RAM. Why is this?

XP only shows useable RAM. With SP1, 32 bit Vista was modified
to show all installed RAM, even if it couldn't use it. The change was
made in Vista to address, "Where did the rest of my RAM go?"
type questions.

 

[Tim Slattery]

I bought a laptop with vista home premium almost two years ago. It had 2 Gb
of RAM. I upgraded it to 4GB of RAM and vista would show the 4GB in the
system properties box. Then I changed to Windows XP Professional and now the
system properties box shows only 2.99 GB of RAM. Why is this?

Any 32-bit system will use only about 3.2 to 3.5GB of RAM. See
http://members.cox.net/slatteryt/RAM.html for a discussion of why this
is so. More recent versions of 32-bit Vista (RC1, I think) will show
all the RAM that's installed, even though they won't use all of it. (I
guess MS got tired of the question constantly coming up.)