Accessable RAM - 32it XP

[Alan T]

No, it's more of a math kind of thing. The processor has a 4GB address

space, the hardware devices reserve whatever they need and the RAM can
have what's leftover. In your example above if the hardware were to need
a total of 2.25GB of space there would only be 1.75GB of space left and
that is all that the RAM would get. This is just an example, I have never
yet seen that much demand being made by the hardware devices, the most I
have ever seen reported by users in these groups was the hardware using
1.75GB and the RAM being left with 2.25GB, that is not often seen, most
reports are that the hardware is using about.75 to 1.25GB, that leaves
about 2.75 to 3.25GB available for the RAM.

For 32bit SP, if I have 2GB RAM, although the OS can access the 2 GB,
however, there may be much less than 2GB 'can' be used by XP?

 

[John John - MVP]

For 32bit SP, if I have 2GB RAM, although the OS can access the 2 GB,
however, there may be much less than 2GB 'can' be used by XP?

I have not yet seen that reported, the least that I have seen is 2.25GB,
it takes quite a set of hardware to get to that point, it would take one
mean set of hardware to see any less than that!

John

 

[Ken Blake, MVP]

A 32 bit OS will show 4.00GB of RAM, but can only utilise 3.75GB of it.

No, it's not all 32-bit operating systems, and 3.75GB is not correct.
Here's what's correct:

All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
address space. That's the theoretical upper limit beyond which you can
not go.

But you can't use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. It's usually around
3.1GB.

Note that the hardware is using the address *space*, not the actual
RAM itself. The rest of the RAM goes unused because there is no
address space to map it too.