I am running 64 bit fedora 8 on 2.6.23.9-85 kernel, system is a 3.2Ghz prescott cpu on an intel 915 chipset mobo and 4GB of memory. when i boot, i can see it says 4096MB, in the bios it also says 4GB, but when in fedora it says 3.5GB, this is the 64bit version. any ideas?

thanks.

Are you using to see the memory? The free program calculates the memory incorrectly. Try running 'free -K' or 'free -M' in the terminal.

The only 3.5GB available memory has little to nothing to do with your Operating System, in this case Fedora.

It is a limitation that came with the implantation of PCI-bus, this system bus needs around 512mb for system addresses. Even cards or addresses you not use are used.

Some newer motherboards have the option to relocate, your 512mb to another address range, so you get 4gb on available. But with every system hack, some of this hacks are not fully compatible and with make computers more unstable. Similar to extended memory boards in our early XT or AT IBM computers. When the ISA bus limited our 1MB to only 640kb.

Anyway, even operating systems like MS Windows XP are limited to use only momory within the 4GB range, so hacks of relocating the memory to another range will not give any additional memory, also for most Linux kernel you need to recompile the kernel with large memory enabled, that is if you can in the BIOS selected relocating the 512MB to a higher range.

My BIOS has a setting to set for 64bit addressing I would check for similar in yours and I would check for sure that you are actually running a 64bit chip/install not many of those older chips could run 64bit. So if you are running 32bit you will most likely never get more than the ram you see now due to 32bit addressing limitations with the memory reserved like the poster above mentions.

Like Dummy-in-Linux said. The reason you aren't seeing all 4G has nothing to do with linux. Windows will do the same. It also has little to do with 32 or 64 bit. The MB bios is you problem. If you have an onboard video card, that's the biggest hitter. They RARELY have their own memory, they just pull some of your system RAM. The BIOS itself sometimes will copy itself to RAM because it's faster than ROM. Also, all of your ports, serial, parallel, USB, IDE, SATA, add on cards ALL want a cut of the pie for their own ROMs to be copied up.

I just had this very same conversation with an Oracle DBA on some very high end IBM servers with 64G. He told me the 64 bit Windows should give him every meg... I had to show him several articles about where it goes.

Phil

If i'm not mistaken thou what he means is just
is that? Sure memory will be taken up by the system, that's what it's there for. But you should still report the correct total. No?