On Fri, Feb 17, 2006 at 01:07:39PM -0500, .:: Awi ::. wrote: > Hi there, > > I install fedora core 4, kernel 2.6.14-1 x86_64 on HP A1250N, AMD64 X2 4GB > RAM. > BIOS reported 4 x 1024 MB ram installed, but linux recognize 3GB only. Your system has likely mapped all 4GB into the lower 4GB of address space. Unfortunatly, there's also a 1GB 'hole' there for PCI devices to map into. The end result is this 'hole' maps over the top of your ram making it inaccessable. Some BIOS's offer a remapping feature (Unfortunatly they all seem to call it something different so you may have to hunt around) that hoists 1GB of your RAM above the 4GB, so your memory map ends up looking like.. |1GB|1GB|1GB|PCI|1GB| There are some boards out there however that don't offer a remapping feature in the BIOS. If this is the case for your board, you're completely out of luck, and your only recourse is to complain to the vendor (or return the system). The reason the bios reports the 4GB without issue is that PCI enumeration is done after RAM initialisation, and the POST never takes into account address space collisions created by other devices on the bus. > I read there is 3GB/1GB issue, user/kernel VM, but I don't get it. > My goal is I can utilize all those 4GB for user, instead of 3GB/1GB. That's unrelated, it only affects 32bit systems. 64bit CPUs have a larger address space, so this isn't the problem. Dave
