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4Gigs of RAM showing as 3.5Gigs

Occasional Contributor

4Gigs of RAM showing as 3.5Gigs

we upgraded our RAM on our Windows 2000 Server on HP PROLIANT DL360G4p to 4Gigs but it only shows 3.5, is there a BIOS setting to adjust this?
Occasional Advisor

Re: 4Gigs of RAM showing as 3.5Gigs


The Hot-Plug PCI Reservation depends on the particular OS being used plus other factors too. Compaq Configuration Utility or RBSU allows the PCI Hot Plug Reservation Option set to either "Normal", which only allocates 32MB (minimum) per hot plug slot, or "Extensive", which allocates 128MB (minimum) RAM per hot plug slot. The default setting for Windows 2003 is "Normal". This is because Windows 2003 can address the entire RAM in the server and is more likely to have contention for memory resources with Hot Added PCI devices.

Please note that RAID controller will reserve the 40MB memory space.

For example:
Normal - 6slots x 40MB (reserved memory space) = 240MB
Extensive - 6slots x 144MB (reserved memory space) = 864 MB

For more information on tuning feature, refer the following Microsoft article:;en-us;291988

Michael Richter
Trusted Contributor

Re: 4Gigs of RAM showing as 3.5Gigs

additinal have a look into this customer advisory