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4GB memory in a 32-bit system, detecting only 2.9GB

asked 2018-01-05 00:36:44 -0600

alfC gravatar image

updated 2018-01-05 14:37:29 -0600

I have a relatively old computer with Fedora 27, Acer Aspire 5610-BL50 with BIOS v3.60 (latests, https://www.acer.com/ac/en/US/content... ). In order to make it work better, I upgraded the memory and I put two DDR2 ram chips with 2GB each, 4GB in total.

However Fedora only detects 2.9GB. I know that perhaps part of the memory is reserved for the video card (which can't be set to zero in the bios), and also since this is a 32-bit, 4GB should be an upper limit.

But still, why I can't use memory above 2.9GB?

Some answers in AskFedora ( https://ask.fedoraproject.org/en/ques... ) suggest video cards can be using the memory, however I doubt it is using a full 1.0GB. This is approximately what I see in the BIOS (photo), and below a bunch of diagnostics from the graphical interface and the command line. (for example uname returns a PAE kernel).

biosacer

$ free -m
              total        used        free      shared  buff/cache   available
Mem:           3018        1659         246         457        1112         945
Swap:          8191         146        8045

$ uname -a
Linux aspire 4.14.8-300.fc27.i686+PAE #1 SMP Wed Dec 20 19:31:13 UTC 2017 i686 i686 i386 GNU/Linux

detailssettings

$ sudo lshw -class memory
  *-firmware                
       description: BIOS
       vendor: Acer
       physical id: 0
       version: V3.60
       date: 08/12/2008
       size: 101KiB
       capacity: 960KiB
       capabilities: pci pcmcia pnp upgrade shadowing escd cdboot bootselect int5printscreen int9keyboard int17printer int10video acpi usb agp smartbattery biosbootspecification
  *-cache
       description: L2 cache
       physical id: 5
       slot: L2 Cache
       size: 2MiB
       capacity: 2MiB
       capabilities: burst internal write-back
       configuration: level=2
  *-memory
       description: System Memory
       physical id: a
       slot: System board or motherboard
       size: 4GiB
     *-bank:0
          description: SODIMM DDR2 Synchronous
          physical id: 0
          slot: M1
          size: 2GiB              <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
          width: 32 bits
     *-bank:1
          description: SODIMM DDR2 Synchronous
          physical id: 1
          slot: M2
          size: 2GiB              <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
          width: 32 bits
  *-memory:0 UNCLAIMED
       description: FLASH memory
       product: ENE PCI Memory Stick Card Reader Controller
       vendor: ENE Technology Inc
       physical id: 4.1
       bus info: pci@0000:06:04.1
       version: 01
       width: 32 bits
       clock: 33MHz (30.3ns)
       capabilities: pm cap_list
       configuration: latency=0 maxlatency=4 mingnt=1
       resources: memory:f0203000-f020307f
  *-memory:1 UNCLAIMED
       description: FLASH memory
       product: FLASH memory: ENE Technology Inc:
       vendor: ENE Technology Inc
       physical id: 4.3
       bus info: pci@0000:06:04.3
       version: 01
       width: 32 bits
       clock: 33MHz (30.3ns)
       capabilities: pm cap_list
       configuration: latency=0 maxlatency=4 mingnt=1
       resources: memory:f0203800-f020387f
  *-memory:2
       description: FLASH memory
       product: SD/MMC Card Reader Controller
       vendor: ENE Technology Inc
       physical id: 4.4
       bus info: pci@0000:06:04.4
       version: 01
       width: 32 bits
       clock: 33MHz (30.3ns)
       capabilities: pm cap_list
       configuration: driver=sdhci-pci latency=0 maxlatency=72 mingnt=32
       resources: irq:17 memory:f0202000-f02020ff

monitor

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Comments

1

Probably a limitation of your Intel 945GM chipset and a sloppy bios. Basically the Memory Controller Hub does not remap Apic or PCI Express memory space and bios designers put a limit of 3GB to addressable ram reserving 1GB for i/o, integrated video card, etc.. They could have calculated the least amount of address space needed, instead they put an hard limit of 1GB. I guess you won't get more than 3GB ram...

fcomida gravatar imagefcomida ( 2018-01-05 05:56:31 -0600 )edit

@fcomida, sloppy hardware seem a likely explanation. Just to be clear, this has nothing to do with a 32bit vs. 64bit OS, right? If I remember correctly I couldn't install 64bit Fedora even if I wanted to.

alfC gravatar imagealfC ( 2018-01-05 14:23:37 -0600 )edit

To answer the 64bits question, it is important to know if the CPU is capable of 64bits instructions. Please show us the relevant output of lscpu

florian gravatar imageflorian ( 2018-01-05 15:10:52 -0600 )edit

2 Answers

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answered 2018-01-05 06:30:09 -0600

Hi, just saw that, the Aspire 5610 is based on the 945GM chipset which has "32-bit interface to address up to 4 GB of memory", so you have a HW limitation on this and 2.9 will be the hard limit on memory allocation. More in Intel chipsets specs

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answered 2018-01-05 03:42:04 -0600

Hi, To detect all the memory on that configuration you need to install the PAE kernel.

Take a look at this thread What is the difference between 32-bit PAE and 64-bit kernels?

Cheers

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Don't I have a PAE kernel if uname returns 4.14.8-300.fc27.i686+PAE #1 SMP (see the complete result of uname in the question).

alfC gravatar imagealfC ( 2018-01-05 04:12:51 -0600 )edit

I think it all makes sense, before I had 1GB + 2GB chip and Fedora was reporting something like 2.6GB. which is probably 3GB - video memory. Now with 2 + 2 GB chip is reporting 2.9GB. (If you convert the comment to an answer I will accept it.)

alfC gravatar imagealfC ( 2018-01-05 14:26:59 -0600 )edit

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Asked: 2018-01-05 00:36:44 -0600

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Last updated: Jan 05 '18