No whole phisical memory, no 64bit

[utu]

Greetings.

This is a puzzling report.

I have a 64-bit Dell 1545 with 4 Gb ram and Knoppix 7.6.1 automatically realizes
and provides a 64-bit kernel which recognizes all the ram. Its a Win7 machine, so it
uses Legacy boot, not uefi.

You might see if you can Legacy boot your machine and get around your problem that way.
I know Win8 Dells have both legacy and uefi boot choices; maybe your machine does as well.

Hope that helps.

[szzsqing1]

My boot is quite different. On my HDD there is not installed any OS. I use only live systems (mainly Knoppix in live mode) run from ISO files copied to HDD. The boot is provided by an installed GRUB2 (made with SystemRescCD) and manually edited grub.cfg file.
But reading your reply I have found the solution.
This was the wrong menuentry in the grub.cfg file:

menuentry "KNOPPIX_V7.6.1DVD-2016-01-16-EN 64b hu London" {
    set ISO=boot-isos/KNOPPIX_V7.6.1DVD-2016-01-16-EN.iso
    loopback loop /$ISO
    linux (loop)/boot/isolinux/linux knoppix64 bootfrom=/dev/sda1/$ISO nostartsound noeject noprompt lang=hu tz=Europe/London --
    initrd (loop)/boot/isolinux/minirt.gz
}

The problem was that I should have used "linux64", not "linux". First I tried "linux64" and "knoppix64" but the system could not started. So here is the good version:

menuentry "KNOPPIX_V7.6.1DVD-2016-01-16-EN 64b hu London" {
    set ISO=boot-isos/KNOPPIX_V7.6.1DVD-2016-01-16-EN.iso
    loopback loop /$ISO
    linux (loop)/boot/isolinux/linux64 knoppix bootfrom=/dev/sda1/$ISO nostartsound noeject noprompt lang=hu tz=Europe/London --
    initrd (loop)/boot/isolinux/minirt.gz
}

Now Knoppix - like SystemRescCD - can see 3,7G.

knoppix@Microknoppix:~$ free -h
              total        used        free      shared  buff/cache   available
Mem:           3,7G        241M        2,5G        143M        999M        3,2G
Swap:          2,7G          0B        2,7G
knoppix@Microknoppix:~$

Thank you for your help.