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I know somebody will mark this as duplicate, but I can't find the answer, so I'm asking. I have 3GB of RAM and Ubuntu says: Memory 2.9 GiB. No, it is NOT my onboard graphics card, because it uses only ONE GiB of RAM.

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  • I have a very similar situation; I have 4 GiB installed and 64-bit Kubuntu, and it reports 3.9 GiB. I always just figured it was "system overhead"; it's still 400 MiB more than I'd get with a non-PAE 32-bit OS. I'll have to watch this question to see what answer you get.
    – Zeiss Ikon
    Dec 30, 2014 at 20:25
  • What does free -m report?
    – SlightlyCuban
    Dec 30, 2014 at 20:26
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    @ZeissIkon you are messing up too: you probably have 4Gb and NOT 4GiB. Memory is NOT sold as GiB. 4Gb is roughly 3.9GiB.
    – Rinzwind
    Dec 30, 2014 at 20:53
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    @Rinzwind, no, memory is sold in GiB
    – psusi
    Dec 31, 2014 at 3:39
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    @Rinzwind RAM has been manufactured and sold in powers of 2 since before I bought my first chips (to be seated in sockets, in banks of 9 to make a 16 KiB page with parity -- upgrading a computer with 16 KiB to 64 KiB). The methods of manufacture and addressing scheme make powers of two the most practical way to deal with this. Mass storage devices, OTOH, have been sold in powers of ten since long before gigabyte drives came out (my first hard disk was 20 MB, and held just under 20 MiB).
    – Zeiss Ikon
    Dec 31, 2014 at 11:14

1 Answer 1

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1GB (1 Gigabyte = 1'000 MB) and 1GiB (1 Gibibyte = 1'024 MiB) aren't the same thing.

You say that you should have 3GB of RAM and the Graphics chip uses 1 GiB.

I assume you have a total of 4GB RAM, of which 1GiB is dedicated the Graphics chip. And what's the result of 4GB-1GiB? That's correct: 2.9GB or 2.73GiB.

I've got the slight feeling that even memory manufacturers don't know the difference between those two unit systems (or they deliberately fool the customers and use them interchangably, so your 4GiB memory actulally only is 4GB, which is 3.72GiB) That Ubuntu says 2.9GiB doesn't sound correct to me. Frontends and their system utils don't always 100%ly match...

So you see, it's always a fuss about those two unit systems. Better not think about it and accept it or you'll end up with a terrible headache...

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    +1 you beat me to this answer. An auto calculator and chart can be found here if the OP, or anyone else, wants more info.... wintelguy.com/gb2gib.html
    – TrailRider
    Dec 30, 2014 at 20:50
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    This needs a little more digging; HD manufacturers tend to go by GB, but RAM manufacturers go by GiB (from Wikipedia). I agree the difference is probably negligible, but I'm not positive this is the correct answer.
    – SlightlyCuban
    Dec 30, 2014 at 20:54
  • Indeed, only HD manufacturers use powers of 10, ram is in powers of 2, so 4 GB of ram is 4 * 1024 * 1024 * 1024 bytes.
    – psusi
    Dec 31, 2014 at 3:38
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    RAM has always been in powers of 2. Google "GB RAM" and you'll find multiple listings of modules as containing 1024 Megabytes; in fact, megabyte originally referred to 1024 * 1024 bytes, and it was false advertising by hard disk makers that brought up the need to distinguish between MB and MiB.
    – Zeiss Ikon
    Dec 31, 2014 at 11:18
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    @ZeissIkon, to be fair, floppy makers also screwed it up, adding to the confusion. 720k disks were 720 KiB, but when they doubled the density to 1440 KiB, they mislabeled them as 1.44 MB, which isn't correct using either base 2 or base 10.
    – psusi
    Dec 31, 2014 at 14:54

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