[CentOS] 4gb ram shows as 3.3gb

[Jeremy Rosengren]

Martin Marques wrote:
> John R Pierce wrote:
>>
>> but thats neither here nor there, PAE is a universal issue for any 
>> x86 32bit system with 4GB+ ram, with PAE disabled, the BIOS, PCI, AGP 
>> or PCI-express, etc IO spaces consume anywheres from .5 to 1GB of the 
>> 32bit address space.   PAE is a hardware workaround implemented in 
>> pretty much all Intel and AMD CPUs made in the last 5+ years, and 
>> allows the OS to access more than 4GB of physical address space.  PAE 
>> introduces some hardware overhead because it involves larger page 
>> tables and another level of indirection in the TLB lookups.
>>
>> CentOS 5 installs defaults to PAE off because there are some systems 
>> where PAE is crash-happy.    Someone here has already explained how 
>> to enable PAE and in fact the original poster tried it and is happy 
>> with his full 4GB now.
>
> Well, looks like I'm having quite a bit of a problem then. :-(
>
> I have PAE kernel running, and all I see is 3.2Gb of the 4Gb.
>
> dmidecode gives me this (intel chip):
>
> Handle 0x0000, DMI type 0, 20 bytes.
> BIOS Information
>         Vendor: Intel Corp.
>         Version: EV91510A.86A.0482.2006.0222.2350
>
> And later this:
>
> Handle 0x0041, DMI type 19, 15 bytes.
> Memory Array Mapped Address
>         Starting Address: 0x00000000000
>         Ending Address: 0x000C77FFFFF
>         Range Size: 3192 MB
>         Physical Array Handle: 0x0040
>         Partition Width: 0
>
> [snip]
>
> Handle 0x0048, DMI type 17, 27 bytes.
> Memory Device
>         Array Handle: 0x0040
>         Error Information Handle: 0x003F
>         Total Width: 64 bits
>         Data Width: 64 bits
>         Size: 1024 MB
>         Form Factor: DIMM
>         Set: 2
>         Locator: J6H2
>         Bank Locator: CHANNEL B DIMM1
>         Type: DDR
>         Type Detail: Synchronous
>         Speed: 400 MHz (2.5 ns)
>         Manufacturer: Manufacturer4
>         Serial Number: SerNum4
>         Asset Tag: AssetTagNum4
>         Part Number: PartNum4
>
> Handle 0x0049, DMI type 20, 19 bytes.
> Memory Device Mapped Address
>         Starting Address: 0x000C0000000
>         Ending Address: 0x000C6FFFFFF
>         Range Size: 112 MB
>         Physical Device Handle: 0x0048
>         Memory Array Mapped Address Handle: 0x0041
>         Partition Row Position: 2
>         Interleave Position: 2
>         Interleaved Data Depth: 2
>
>
> As you can see, the last 1Gb bank is only used at 11%.
>
> Any ideas on why I can't see all 4Gb?
>
This thread may be a start:  http://lkml.org/lkml/2006/7/26/204

It sounds like this is a problem with this particular chipset.

-- jeremy