Re: 4GB RAM support

Well put. The point I make is that if a hardware device had its own memory
the 4GB addressing need not be more than 4GB. Common sense.
<j.n@xxxxxxxxxx> wrote in message
news:B3K_i.3097$sm1.2996@xxxxxxxxxxxxxxxxxxxxxxx

"John John" <audetweld@xxxxxxxxxxx> wrote in message
news:O7%238hYuJIHA.4880@xxxxxxxxxxxxxxxxxxxxxxx
For the benefit of other who may be reading this is the reason why the
user cannot see and use all the RAM in his machine.


The hardware memory issue is summed up as so by Tyan:

[Quote]

The problem that you are seeing is based on an older architecture
design for memory addressing. All the systems architecture up to this
point were based on a maximum of 4GB of total memory. Nobody really
thought, when this standard was designed, that this amount of memory
would actually be in use. The problem that has happened is that you
have PCI devices that require memory address ranges so that they can
properly execute their commands. These address ranges were mapped in
the upper sections of this maximum amount. Since nobody thought you
would be using up to 4GB these address ranges started around the last
500MB of the memory ranges. This range is called the T.O.M. or Top of
Memory range. This is the point in the bios where it places on hold the
amount of memory that is required by the various PCI devices that are
found on the motherboard. Thus when you have PCI cards or AGP cards
installed on your motherboard these devices hold on to memory for their
own use and take away from the maximum amount of memory that is
available for other tasks. This amount of memory can vary from a little
as 200MB all the way to 1GB of memory (or even more in select cases).
It just depends on the PCI devices you have and the amount of PCI
(including AGP) that you have installed all at once.

There is really no way to get around this basic design limitation. The
only way to get around these type of issues is to use certain new
designs that have brand new architectures (i.e 64-bit designs) that
allow memory to be mapped in area's above 4GB. The brand new Intel Xeon
designs and the AMD Opteron designs are built around 64-bit technology.
This is only ½ of the equation that you would need to find success.
You would also need to use an OS that is actually PAE or PAE aware so
that it is able to address memory above the 4GB level. To find out
about PAE you can search Microsofts website for PAE (Physical Address
Extensions) and it will explain this concept and what OS's actually are
capable of providing this benefit. Windows 2000 and Windows 2003 would
fit both of these criteria. Windows XP on the hand would not allow this
type of ability.

Microsoft has addressed this type of issue in the following Microsoft
Article (291988)
http://support.microsoft.com/default.aspx?scid=kb;en-us;291988

[End quote]

http://www.tyan.com/archive/support/html/memory_faq.html

This is exactly what I said in my earlier post, so now get lost or go
take a Remedial Reading course you troll!

John

Unknown wrote:

Your description is completely wrong. 32 bits can address 4GB but the
address can be used for any device attached to the computer---a HD for
example. The reason there is only 3GB of memory is because the 1 GB is
reserved for items
that use DMA for example.

"John John" <audetweld@xxxxxxxxxxx> wrote in message
news:ODdYr$kJIHA.2480@xxxxxxxxxxxxxxxxxxxxxxx

Other than moving to a 64-bit operating system there isn't much that you
can do to see and use the last GB of RAM. What is happening is that
32-bit Windows can only address 4GB of memory, the addressable memory is
insufficient to supply all your devices so the RAM cannot fully be used.
Memory above doesn't mean RAM only, it is memory addressing for all the
devices installed in the computer. For example, if you have 4GB of RAM
and a video card with 512MB of memory, your addressing requirements are
for 4.5GB but 32-bit Windows can only address 4GB, the memory addresses
are reserved for devices before the RAM so 512MB of addressing space
used for the video card is unavailable for other devices, the remaining
addressing space is only 3.5GB so you won't be able to fully use the 4GB
of installed RAM. In your case the addressing requirements for your
hardware is about 1GB, so these addresses are not available to the
installed RAM, you need about 5GB of memory addresses but 32-bit Windows
can only address 4GB, after the hardware addressing requirements are met
there is only 3GB of addresses left so you cannot fully use the
installed RAM in your machine.

John

John wrote:


Hi all,

I just got tablet pc with 4GB RAM but I only can see 3GB. Is this
supposed to be?
if not, how do I make it to see 4GB RAM?

Thanks.




In short, the "problem" is caused by memory mapped i/o.
Jim



.

Relevant Pages

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