[CentOS] 4gb ram shows as 3.3gb
jeremy at rosengren.org
Thu Jul 26 21:58:54 UTC 2007
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
> 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.
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