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  1. In Lubuntu 18.04 in a laptop (Model Name: SATELLITE C55DT-A5244), free shows its RAM ram is 3.3G

    $ free -h
              total        used        free      shared  buff/cache   available
Mem:           3.3G        1.2G        444M         46M        1.7G        1.8G

    while lshw shows the RAM should be 4GiB

     *-memory
      description: System Memory
      physical id: d
      slot: System board or motherboard
      size: 4GiB
    *-bank:0
         description: SODIMM DDR3 Synchronous Unbuffered (Unregistered) 533 MHz (1.9 ns)
         product: M471B5673FH0-CF8
         vendor: Samsung
         physical id: 0
         serial:  
         slot: DIMM 0
         size: 2GiB
         width: 64 bits
         clock: 533MHz (1.9ns)
    *-bank:1
         description: SODIMM DDR3 Synchronous Unbuffered (Unregistered) 800 MHz (1.2 ns)
         product: M471B5773CHS-CK0
         vendor: Samsung
         physical id: 1
         serial: 
         slot: DIMM 1
         size: 2GiB
         width: 64 bits
         clock: 800MHz (1.2ns)

    Why do the 3.3G and 4GiB differ? The difference between 4GiB i.e. 4.29497 GB, and 3.3G is 0.99GB, i.e. 990MB.

    The two RAM chips have different frequencies: 533MHz and 800MHz. Can that be a problem? What frequencies should the two RAM chips be?

  2. In another Thinkpad T400 laptop, under Lubuntu 18.04, free and lshw also don't report the same RAM size, though with difference smaller than the previous laptop: free shows 7.7G RAM, and lshw shows 8GiB RAM from two RAM chips of the same frequency. The difference between 8GiB i.e. 8.58993 GB, and 7.7G is 0.89GB, i.e. 890MB.

     *-memory
      description: System Memory
      physical id: 2b
      slot: System board or motherboard
      size: 8GiB
    *-bank:0
         description: SODIMM DDR3 Synchronous 1066 MHz (0.9 ns)
         product: SUPERTALENT02
         vendor: 8634
         physical id: 0
         serial: 00000000
         slot: DIMM 1
         size: 4GiB
         width: 64 bits
         clock: 1066MHz (0.9ns)
    *-bank:1
         description: SODIMM DDR3 Synchronous 1066 MHz (0.9 ns)
         product: SUPERTALENT02
         vendor: 8634
         physical id: 1
         serial: 00000000
         slot: DIMM 2
         size: 4GiB
         width: 64 bits
         clock: 1066MHz (0.9ns)

Thanks.

Tim
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    You are comparing GB with GiB. The one is decimal, the other binary. Plus your graphics card probably gets a bit of RAM. Use free --gibi. – Rinzwind Apr 02 '19 at 13:59
  • Thanks. How can I find out the amount of system RAM that's shared to the built-in graphics adapter? – Tim Apr 02 '19 at 14:09
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    This is the THIRD time that you've asked about memory here. Listen closely to the answers you've received before. https://askubuntu.com/questions/1130619/how-could-i-find-out-the-requirements-on-rams-that-can-work-with-a-laptop and https://askubuntu.com/questions/1118684/what-are-the-model-current-ram-size-and-max-ram-size-supported-by-this-laptop?noredirect=1&lq=1 – heynnema Apr 02 '19 at 14:26
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    Possible duplicate of How could I find out the requirements on RAMs that can work with a laptop? – heynnema Apr 02 '19 at 14:31
  • @heynnema Are the questions about RAM the same? Can I beg you please bother to read and understand what the questions are about, before blindly accusing dupliates? Please be friendly, respectful, inclusive, accepting. Much apprecated. I am in a very bad situation, and feel I am dying when I have to argue over these kinds of things. – Tim Apr 02 '19 at 14:35
  • You've asked similar questions since Feb 2019. Are you really looking to expand your RAM? Get the correct model # from the tag that's on the bottom of your laptop (not lshw), then go to crucial.com. – heynnema Apr 02 '19 at 14:43
  • @hey I am, but I am in very tight budget and a very bad situation, which explains why I hesitate. – Tim Apr 02 '19 at 14:57
  • https://www.crucial.com/usa/en/compatible-upgrade-for/Toshiba/satellite-c55dt-a5244 – heynnema Apr 02 '19 at 15:00

1 Answers1

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In both cases, the difference is probably the amount of system RAM that's shared to the built-in graphics adapter. There is also some amount of RAM taken by the OS that doesn't show (it's usually a small amount, and varies depending on a number of factors, including kernel version and compiled-in drivers). This RAM isn't shown by free because it's not available for the OS to use at any time, but lshw is examining the hardware information, not the BIOS/OS reported RAM figures.

Zeiss Ikon
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  • The rest of the difference is the difference between power of 1000 and 1024. Use free -h --si for * 1024 – pLumo Apr 02 '19 at 14:01
  • Thanks. How can I find out the amount of system RAM that's shared to the built-in graphics adapter? – Tim Apr 02 '19 at 14:06
  • Generally, subtraction will do the job. With modern chipsets, it'll be a multiple of 128 MB. Usually this is user configurable in BIOS setup, so looking there for what it's set at is a good check. – Zeiss Ikon Apr 02 '19 at 14:37
  • @ZeissIkon Do you mean the amount of system RAM that's shared to the built-in graphics adapter? Can I find it out without restarting my Lubuntu? – Tim Apr 02 '19 at 14:42
  • Given that graphics are generally the only thing that will take away from system RAM, getting the two figures in the same units (GB or GiB) and subtracting one from the other will give the result. Other than that, I don't offhand know a way to explicitly display the graphics RAM amount (though I'm pretty sure there is one). – Zeiss Ikon Apr 02 '19 at 14:54
  • Thanks. Both two laptops run 64-bit Lubuntu 18.04 and the differences are not " 256 MB or 384 MB" as in your reply: (1) In the first laptop: lshw shows 4GiB i.e. 4.29497 GB, and free shows 3.3G. Their difference is 0.99GB, i.e. 990MB. (2) In the second laptop: lshw shows 8GiB i.e. 8.58993 GB, and free shows 7.7G. Their difference is 0.89GB, i.e. 890MB. – Tim Apr 02 '19 at 18:51
  • Is that machine running 32-bit or 64-bit Ubuntu? 32-bit without the HWE layer will only "see" 3.5 GiB max. – Zeiss Ikon Apr 02 '19 at 18:53
  • Which reports "the BIOS/OS reported RAM figures", free or lshw? – Tim Apr 02 '19 at 19:12