Fedora 64bit and Ubuntu 12.04 64bit sees 7.8GiB when i have 8GB

[snowcake]

Hello, I recently using Ubuntu 12.04 64bit and i like it.

Windows and memtest86 both are saying i have 8155MB for full use. And windows say i have 8gb on computer properties.

Ubuntu says i have 7.8GiB in system monitor. I also booted Fedora 64bit live cd and it says the same thing.
AND the strange thing is that Ubuntu 32bit says i have 7.9GiB vs 7.8GiB in Ubuntu 64bit.

Why all this?? As far as i can tell, there is nothing wrong with my memory.
I also use a dedicated GPU, so no igp is stealing my memory.

How much ram memory having you all in system monitor?
Does it also display less memory than in windows or memtest? Assuming you have no igp.

I am really worried since this is a new pc.


Thanks,

 

[hhhd1]

You are worrying to much over nothing.

you have 8 gegabytes of ram = 8,192 MBs

memtest showing 8155MB, which means that there are few MBs reserved by the system board.

windows is showing the total size of ram modules, ignoring the 1% reserved space.

ubuntu is showing 8155 MB=7.96 GB (like memtest)

ubuntu 64 is showing a little bit less than that, which is ok-ish imo (i do not know why, but i wouldn't worry to much about it, might be reserved by the kernel or something).

Every OS is adding a little bit of tweaks to the ram size displayed.

 

[snowcake]

You are worrying to much over nothing.

you have 8 gegabytes of ram = 8,192 MBs

memtest showing 8155MB, which means that there are few MBs reserved by the system board.

windows is showing the total size of ram modules, ignoring the 1% reserved space.

ubuntu is showing 8155 MB=7.96 GB (like memtest)

ubuntu 64 is showing a little bit less than that, which is ok-ish imo (i do not know why, but i wouldn't worry to much about it, might be reserved by the kernel or something).

Every OS is adding a little bit of tweaks to the ram size displayed.

What ubuntu 32bit is showing in hardinfo that i have: of 8235888kb=7.85GB
That is not as much as you says.

How can this be?

 

[shabby]

How can this be?

 

[tweakboy]

That is how all storage is, thats how windows works.

If you buy a 500GB HD you have like 477GB free to start off with.

Flash drive 8GB will show 7.x gl

 

[Cerb]

That is how all storage is, thats how windows works.

If you buy a 500GB HD you have like 477GB free to start off with.

Flash drive 8GB will show 7.x gl

No, it's not. That is just non-volatile storage. RAM uses real 2^x values, and none is reserved (an 8GB flash drives has 8GB flash, you just don't get to use it all, FI).

 

[Eeqmcsq]

It's very likely that the amount of total RAM in Ubuntu's system monitor comes from /proc/meminfo. You can read its contents by doing a:

cat /proc/meminfo

The 1st line is the MemTotal, and according to this site:

http://unixfoo.blogspot.com/2008/02/know-about-procmeminfo.html

MemTotal: Total usable RAM in kilobytes (i.e. physical memory minus a few reserved bytes and the kernel binary code)

So most likely, the missing RAM is the result of the kernel being loaded into physical RAM. Which I suppose makes sense, because you'd assume that a 32-bit kernel would eat up less physical RAM than a 64-bit kernel.

It's also possible that the BIOS is reserving some physical RAM for its own uses. You can see the "BIOS-provided physical RAM map" by doing a:

dmesg | more

Example map from one of my old computers with a discrete video card with 3 GiB of RAM, ubuntu-32 10.04;

[    0.000000] BIOS-provided physical RAM map:
[    0.000000]  BIOS-e820: 0000000000000000 - 000000000009dc00 (usable)
[    0.000000]  BIOS-e820: 000000000009dc00 - 00000000000a0000 (reserved)
[    0.000000]  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
[    0.000000]  BIOS-e820: 0000000000100000 - 00000000bfff0000 (usable)
[    0.000000]  BIOS-e820: 00000000bfff0000 - 00000000bfff3000 (ACPI NVS)
[    0.000000]  BIOS-e820: 00000000bfff3000 - 00000000c0000000 (ACPI data)
[    0.000000]  BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)

The physical RAM map is somewhere near the beginning of the output of dmesg. I have no clue how to read this map, but I'm guessing that you'll see some ranges of addresses reserved, and my guess is that this cuts into the amount of RAM available to the OS.

Basically, if your available RAM is reasonably close to your physical RAM, you're good.