"Ron Hardin" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Conor wrote:
>>
>> In article <(E-Mail Removed)>, Ron Hardin says...
>>
>> > Is it that the hardware uses the memory for something (in which case 64
>> > bits
>> > wouldn't help), or that a portion of the address space is occupied by
>> > the
>> > hardware (in which case the OS's virtual memory mapping ought to take
>> > care of
>> > it, if done right, so long as no process wants all 4gb to itself, but
>> > perhaps
>> > it is not done right).
>> >
>> The hardware has it's own memory or range of addresses it needs to
>> reserve to access it. As XP 32 bit can only address 4GB and nothing
>> above this, the mapping is done so the hardware requirements are kept
>> within this 4GB address range.
>
> Don't they have memory management? The user could have the full 4GB
> address space
> with only the OS addressing the hardware devices themselves (the user
> accesses
> falling into actual RAM). That's what I meant by doing it right.
>
> --
> Ron Hardin
> (E-Mail Removed)
>
> On the internet, nobody knows you're a jerk.
Of course, they have memory management. What the OP wants to know is why XP
tells him that there is far less RAM on his system than the 4 GB that he has
installed.
The answer is that RAM gets diverted to such things as shared memory
graphics cards, etc., before XP starts. Exactly how much gets diverted
depends on the system.
This RAM is the pure untouched physical quantity.
Your belief that somewhow there is a way to let the user have full access to
all, or nearly all, of the RAM is false.
The operating system requires quite a bit of memory in addition to the
amount needed for the physical devices for such tasks as memory management.
In fact, the entire operating system is mapped into the virtual address
space that each process owns.
Jim