4 Gig in new Prec 490 showing as 3 Gig?

[john.abreau at zuken.com (John Abreau)]

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Scott Ehrlich wrote:
> I have 4 gig RAM installed in a brand new Dell Precision Workstation 490
> (BIOS confirms this) but both Win XP 32-bit and Knoppix 5.1.1 show 3 Gig
> available.
> 
> What happened to the last 1 gig of memory?


I ran into this about a month ago; here's what Dell's support said:


> Actually, your system is functioning normally. There are two main
> reasons why the system will report less than 4GB of memory. First
> of all, the system reserves 500MB of memory just to operate the
> PCI-Express bus at its full potential. More memory is reserved for
> other integrated devices. On top of that, Windows XP Professional
> (and any 32-bit operating system) has memory reporting limitations
> at 4GB of memory.


> The processor only has 32 address lines, limiting it to an
> addressing map of 4 gigabytes. The chipset, PCI devices,
> PCI express region, and video cards use some of this map,
> and the BIOS correctly reports this range as unavailable to
> the operating system. If the user installs 4 GB of physical
> memory, then the processor has no way to address the memory
> that overlaps with these regions, already in use. The chipset
> directs memory access to the appropriate device rather than
> sending it to random access memory (RAM). On Dell's new line
> of desktops, PCI express uses 500 megabytes (MB) in the map;
> integrated video takes 256 MB right below PCI express, leaving
> 3.25 GB of memory available to the operating system via RAM. In
> some cases, less RAM is available depending on what other add-in
> cards are installed. For more information about virtual memory
> limitations, refer to Microsoft Knowledge Base Article: 294418 -
> "Comparison of 32-Bit and 64-Bit Memory Architecture"





- --
John Abreau
IT Manager
Zuken USA
238 Littleton Rd., Suite 100
Westford, MA 01886
T: 978-392-1777            F: 978-692-4725
M: 978-764-8934
E: John.Abreau at zuken.com  W: www.zuken.com
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