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