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I have just installed Ubuntu 14.04 64-bit on my laptop and on the system monitor it only shows 7.2 GB of RAM and not 8 GB.

Why is that?

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closed as unclear what you're asking by Braiam, terdon, Sneetsher, dobey, Avinash Raj May 6 at 3:20

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What are your PC specs? Graphics card? Notebook or Desktop PC? –  Cornelius May 5 at 17:22
    
800 Mb reserved for your video card. –  Rinzwind May 5 at 17:53
    
768 MB reserved for the video card, most likely. 800 MB is a weird number and the calculation is probably off a bit (or not showing enough precision in decimal places), as it should show 7.25 GB, as 0.75 GB (768 MB) would be reserved for video. –  dobey May 5 at 17:57
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Also, I'm certain this is a duplicate question of "why only XX.Y GB of RAM shown" but I can't seem to find it at the moment. –  dobey May 5 at 17:57
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That question is way too new to be what I was thinking of (system RAM allocated to video has been around for a very long time). 14.04 is not the first time it would have been asked. –  dobey May 5 at 20:46

1 Answer 1

up vote 1 down vote accepted

This is likely to be caused by different understandings of what 1GB, 1MB and what 1KB is.

1KB could mean 1024 bytes or 1000 bytes. The same is true for MB, GB, TB etc. In this case I guess that the manufacturer defined one KB as 1000 bytes (and so on), but in the System Monitor 1KB is defined as 1024 bytes.

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2  
This is not so. Memory size is always calculated by octal values. –  dobey May 5 at 17:52
    
I just found a Wikipedia article about this (en.wikipedia.org/wiki/Kilobyte). If I am understanding everything (Wikipedia and You) right memory is calculated by binary values. Please feel free to correct me, I am not an expert and my knowledge is not too big in this topic... –  Kai May 5 at 17:58
    
Memory (RAM) is always calculated as 8 bits == 1 byte. (That is octal, not binary. Everything is always binary, because a bit is binary, and everything is made up of bits.) –  dobey May 5 at 18:01
    
That is of course like this, but after 1 byte everything is measured in KB, where 1KB could be 1024 bytes or 1000 bytes, right? –  Kai May 5 at 18:04
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@dobey No. One kilobyte (kB) is always 1000 bytes (because kilo derives from the Greek word for thousand). One kibibyte(kiB) is always 1024 bytes. [According to the international standard] Unfortunately the two terms got mixed up by people who thought it convenient to misuse a well known prefix. If some application swaps these meaning then it's fault of the developer ignorance. –  Bakuriu May 5 at 18:04

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