Pela primeira vez espero que não esteja certo. Verifique este link link onde alguém escreve apenas sua máquina suporta 4 × 1GB = 4GB de RAM
Talvez seja necessária / disponível uma atualização do BIOS / firmware?
O BIOS detecta bem e mostra 8GB. Mesmo o lshw mostra 8GB de memória, mas de alguma forma apenas 3.6GB é utilizável.
Saída do uname -a
Linux Prod 2.6.38-15-generic #59-Ubuntu SMP Fri Apr 27 16:03:32 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
free -m
total used free shared buffers cached
Mem: 3646 3047 598 0 164 1126
-/+ buffers/cache: 1756 1889
Swap: 1950 0 1950
Saída do cat / proc / meminfo
cat /proc/meminfo
MemTotal: 3734456 kB
MemFree: 603272 kB
Buffers: 161716 kB
Cached: 1146076 kB
SwapCached: 0 kB
Active: 2027604 kB
Inactive: 847844 kB
Active(anon): 1568608 kB
Inactive(anon): 11472 kB
Active(file): 458996 kB
Inactive(file): 836372 kB
Unevictable: 32 kB
Mlocked: 32 kB
SwapTotal: 1997820 kB
SwapFree: 1997820 kB
Dirty: 224 kB
Writeback: 0 kB
AnonPages: 1567788 kB
Mapped: 171708 kB
Shmem: 12432 kB
Slab: 105832 kB
SReclaimable: 84272 kB
SUnreclaim: 21560 kB
KernelStack: 3248 kB
PageTables: 35304 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 3865048 kB
Committed_AS: 3796728 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 110684 kB
VmallocChunk: 34359623932 kB
HardwareCorrupted: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 47648 kB
DirectMap2M: 3751936 kB
Saída do lshw
description: Mini Tower Computer
product: Dell DM051
vendor: Winbond Electronics
serial: DJFK62J
width: 64 bits
capabilities: smbios-2.3 dmi-2.3 vsyscall64 vsyscall32
configuration: administrator_password=enabled boot=normal chassis=mini-tower power-on_password=enabled uuid=44454C4C-4A00-1046-804B-C4C04F36324A
*-core
description: Motherboard
product: 0WG261
vendor: Winbond Electronics
physical id: 0
serial: ..CN69861613155F.
*-firmware
description: BIOS
vendor: Winbond Electronics
physical id: 0
version: A04
date: 02/03/2006
size: 64KiB
capacity: 448KiB
capabilities: pci pnp apm upgrade shadowing cdboot bootselect edd int13floppytoshiba int5printscreen int9keyboard int14serial int17printer acpi usb ls120boot biosbootspecification netboot
*-cpu
description: CPU
product: Intel(R) Pentium(R) 4 CPU 2.80GHz
vendor: Intel Corp.
physical id: 400
bus info: cpu@0
slot: Microprocessor
size: 2800MHz
capacity: 4GHz
width: 64 bits
clock: 800MHz
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx x86-64 constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl cid cx16 xtpr lahf_lm
*-cache:0
description: L1 cache
physical id: 700
size: 16KiB
capacity: 16KiB
capabilities: internal write-back data
*-cache:1
description: L2 cache
physical id: 701
size: 1MiB
capacity: 1MiB
capabilities: internal varies unified
*-memory
description: System Memory
physical id: 1000
slot: System board or motherboard
size: 8GiB
*-bank:0
description: DIMM DDR Synchronous 533 MHz (1.9 ns)
vendor: Kingston
physical id: 0
serial: 6827D91E
slot: DIMM_1
size: 2GiB
width: 64 bits
clock: 533MHz (1.9ns)
*-bank:1
description: DIMM DDR Synchronous 533 MHz (1.9 ns)
vendor: Kingston
physical id: 1
serial: 2A27E813
slot: DIMM_3
size: 2GiB
width: 64 bits
clock: 533MHz (1.9ns)
*-bank:2
description: DIMM DDR Synchronous 533 MHz (1.9 ns)
vendor: Kingston
physical id: 2
serial: 2A27D213
slot: DIMM_2
size: 2GiB
width: 64 bits
clock: 533MHz (1.9ns)
*-bank:3
description: DIMM DDR Synchronous 533 MHz (1.9 ns)
vendor: Kingston
physical id: 3
serial: 69270C1F
slot: DIMM_4
size: 2GiB
width: 64 bits
clock: 533MHz (1.9ns)
*-pci
description: Host bridge
product: 82945G/GZ/P/PL Memory Controller Hub
vendor: Intel Corporation
physical id: 100
bus info: pci@0000:00:00.0
version: 02
width: 32 bits
clock: 33MHz
*-pci:0
description: PCI bridge
product: 82945G/GZ/P/PL PCI Express Root Port
vendor: Intel Corporation
physical id: 1
bus info: pci@0000:00:01.0
version: 02
width: 32 bits
clock: 33MHz
capabilities: pci pm msi pciexpress normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:40 ioport:d000(size=4096) memory:efd00000-efefffff ioport:ec000000(size=33554432)
*-display:0
description: VGA compatible controller
product: RV370 5B60 [Radeon X300 (PCIE)]
vendor: ATI Technologies Inc
physical id: 0
bus info: pci@0000:01:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=radeon latency=0
resources: irq:43 memory:ec000000-edffffff memory:efde0000-efdeffff ioport:dc00(size=256) memory:efe00000-efe1ffff
*-display:1 UNCLAIMED
description: Display controller
product: RV370 [Radeon X300SE]
vendor: ATI Technologies Inc
physical id: 0.1
bus info: pci@0000:01:00.1
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress bus_master cap_list
configuration: latency=0
resources: memory:efdf0000-efdfffff
*-multimedia
description: Audio device
product: N10/ICH 7 Family High Definition Audio Controller
vendor: Intel Corporation
physical id: 1b
bus info: pci@0000:00:1b.0
version: 01
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list
configuration: driver=HDA Intel latency=0
resources: irq:42 memory:efffc000-efffffff
*-pci:1
description: PCI bridge
product: N10/ICH 7 Family PCI Express Port 1
vendor: Intel Corporation
physical id: 1c
bus info: pci@0000:00:1c.0
version: 01
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:41 ioport:1000(size=4096) memory:efc00000-efcfffff ioport:f4000000(size=2097152)
*-usb:0
description: USB Controller
product: N10/ICH 7 Family USB UHCI Controller #1
vendor: Intel Corporation
physical id: 1d
bus info: pci@0000:00:1d.0
version: 01
width: 32 bits
clock: 33MHz
capabilities: uhci bus_master
configuration: driver=uhci_hcd latency=0
resources: irq:21 ioport:ff80(size=32)
*-usb:1
description: USB Controller
product: N10/ICH 7 Family USB UHCI Controller #2
vendor: Intel Corporation
physical id: 1d.1
bus info: pci@0000:00:1d.1
version: 01
width: 32 bits
clock: 33MHz
capabilities: uhci bus_master
configuration: driver=uhci_hcd latency=0
resources: irq:22 ioport:ff60(size=32)
*-usb:2
description: USB Controller
product: N10/ICH 7 Family USB UHCI Controller #3
vendor: Intel Corporation
physical id: 1d.2
bus info: pci@0000:00:1d.2
version: 01
width: 32 bits
clock: 33MHz
capabilities: uhci bus_master
configuration: driver=uhci_hcd latency=0
resources: irq:18 ioport:ff40(size=32)
*-usb:3
description: USB Controller
product: N10/ICH 7 Family USB UHCI Controller #4
vendor: Intel Corporation
physical id: 1d.3
bus info: pci@0000:00:1d.3
version: 01
width: 32 bits
clock: 33MHz
capabilities: uhci bus_master
configuration: driver=uhci_hcd latency=0
resources: irq:23 ioport:ff20(size=32)
*-usb:4
description: USB Controller
product: N10/ICH 7 Family USB2 EHCI Controller
vendor: Intel Corporation
physical id: 1d.7
bus info: pci@0000:00:1d.7
version: 01
width: 32 bits
clock: 33MHz
capabilities: pm debug ehci bus_master cap_list
configuration: driver=ehci_hcd latency=0
resources: irq:21 memory:ffa80800-ffa80bff
*-pci:2
description: PCI bridge
product: 82801 PCI Bridge
vendor: Intel Corporation
physical id: 1e
bus info: pci@0000:00:1e.0
version: e1
width: 32 bits
clock: 33MHz
capabilities: pci subtractive_decode bus_master cap_list
resources: ioport:c000(size=4096) memory:efb00000-efbfffff
*-network
description: Ethernet interface
product: N10/ICH 7 Family LAN Controller
vendor: Intel Corporation
physical id: 8
bus info: pci@0000:03:08.0
logical name: eth0
version: 01
serial: 00:13:72:b1:12:43
size: 100Mbit/s
capacity: 100Mbit/s
width: 32 bits
clock: 33MHz
capabilities: pm bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=e100 driverversion=3.5.24-k2-NAPI duplex=full firmware=N/A ip=192.168.0.77 latency=64 link=yes maxlatency=56 mingnt=8 multicast=yes port=MII speed=100Mbit/s
resources: irq:20 memory:efbff000-efbfffff ioport:ccc0(size=64)
*-isa
description: ISA bridge
product: 82801GB/GR (ICH7 Family) LPC Interface Bridge
vendor: Intel Corporation
physical id: 1f
bus info: pci@0000:00:1f.0
version: 01
width: 32 bits
clock: 33MHz
capabilities: isa bus_master cap_list
configuration: latency=0
*-ide:0
description: IDE interface
product: 82801G (ICH7 Family) IDE Controller
vendor: Intel Corporation
physical id: 1f.1
bus info: pci@0000:00:1f.1
logical name: scsi0
version: 01
width: 32 bits
clock: 33MHz
capabilities: ide bus_master emulated
configuration: driver=ata_piix latency=0
resources: irq:16 ioport:1f0(size=8) ioport:3f6 ioport:170(size=8) ioport:376 ioport:ffa0(size=16)
*-cdrom:0
description: DVD reader
product: DVD-ROM TS-H352C
vendor: TSSTcorp
physical id: 0.0.0
bus info: scsi@0:0.0.0
logical name: /dev/cdrom
logical name: /dev/dvd
logical name: /dev/scd0
logical name: /dev/sr0
version: DE02
capabilities: removable audio dvd
configuration: ansiversion=5 status=nodisc
*-cdrom:1
description: CD-R/CD-RW writer
product: CD-RW CRX217E
vendor: SONY
physical id: 0.1.0
bus info: scsi@0:0.1.0
logical name: /dev/cdrom1
logical name: /dev/cdrw1
logical name: /dev/scd1
logical name: /dev/sr1
version: 1DS2
capabilities: removable audio cd-r cd-rw
configuration: ansiversion=5 status=nodisc
*-ide:1
description: IDE interface
product: N10/ICH7 Family SATA IDE Controller
vendor: Intel Corporation
physical id: 1f.2
bus info: pci@0000:00:1f.2
logical name: scsi2
version: 01
width: 32 bits
clock: 66MHz
capabilities: ide pm bus_master cap_list emulated
configuration: driver=ata_piix latency=0
resources: irq:20 ioport:fe00(size=8) ioport:fe10(size=4) ioport:fe20(size=8) ioport:fe30(size=4) ioport:fea0(size=16) memory:f4200000-f42003ff
*-disk
description: ATA Disk
product: ST380819AS
vendor: Seagate
physical id: 0.0.0
bus info: scsi@2:0.0.0
logical name: /dev/sda
version: 8.04
serial: 5MR6FVHF
size: 74GiB (80GB)
capabilities: partitioned partitioned:dos
configuration: ansiversion=5 signature=0008bd03
*-volume:0
description: EXT3 volume
vendor: Linux
physical id: 1
bus info: scsi@2:0.0.0,1
logical name: /dev/sda1
logical name: /boot
version: 1.0
serial: be85d45c-4ab6-457c-8ab6-009098158232
size: 476MiB
capacity: 476MiB
capabilities: primary bootable journaled extended_attributes recover ext3 ext2 initialized
configuration: created=2012-04-30 17:49:56 filesystem=ext3 modified=2012-05-15 15:46:35 mount.fstype=ext3 mount.options=rw,relatime,errors=continue,commit=5,barrier=0,data=ordered mounted=2012-05-15 15:46:35 state=mounted
*-volume:1
description: EXT4 volume
vendor: Linux
physical id: 2
bus info: scsi@2:0.0.0,2
logical name: /dev/sda2
logical name: /
version: 1.0
serial: fae37d7d-cc93-4718-9cfb-9aafd4a820c7
size: 19GiB
capacity: 19GiB
capabilities: primary journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized
configuration: created=2012-04-30 17:49:58 filesystem=ext4 lastmountpoint=/ modified=2012-05-07 07:19:32 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,barrier=1,data=ordered mounted=2012-05-16 08:02:52 state=mounted
*-volume:2
description: Extended partition
physical id: 3
bus info: scsi@2:0.0.0,3
logical name: /dev/sda3
size: 54GiB
capacity: 54GiB
capabilities: primary extended partitioned partitioned:extended
*-logicalvolume:0
description: Linux filesystem partition
physical id: 5
logical name: /dev/sda5
logical name: /home
capacity: 53GiB
configuration: mount.fstype=ext4 mount.options=rw,relatime,barrier=1,data=ordered state=mounted
*-logicalvolume:1
description: Linux swap / Solaris partition
physical id: 6
logical name: /dev/sda6
capacity: 1951MiB
capabilities: nofs
*-serial UNCLAIMED
description: SMBus
product: N10/ICH 7 Family SMBus Controller
vendor: Intel Corporation
physical id: 1f.3
bus info: pci@0000:00:1f.3
version: 01
width: 32 bits
clock: 33MHz
configuration: latency=0
resources: ioport:ece0(size=32)
*-scsi
physical id: 1
bus info: usb@1:3
logical name: scsi4
capabilities: emulated scsi-host
configuration: driver=usb-storage
*-disk:0
description: SCSI Disk
product: USB HS-CF Card
vendor: TEAC
physical id: 0.0.0
bus info: scsi@4:0.0.0
logical name: /dev/sdb
version: 4.00
capabilities: removable
*-medium
physical id: 0
logical name: /dev/sdb
*-disk:1
description: SCSI Disk
product: USB HS-xD/SM
vendor: TEAC
physical id: 0.0.1
bus info: scsi@4:0.0.1
logical name: /dev/sdc
version: 4.00
capabilities: removable
*-medium
physical id: 0
logical name: /dev/sdc
*-disk:2
description: SCSI Disk
product: USB HS-MS Card
vendor: TEAC
physical id: 0.0.2
bus info: scsi@4:0.0.2
logical name: /dev/sdd
version: 4.00
serial: 3
capabilities: removable
*-medium
physical id: 0
logical name: /dev/sdd
*-disk:3
description: SCSI Disk
product: USB HS-SD Card
vendor: TEAC
physical id: 0.0.3
bus info: scsi@4:0.0.3
logical name: /dev/sde
version: 4.00
capabilities: removable
*-medium
physical id: 0
logical name: /dev/sde
Saída do sudo dmidecode
http://pastebin.com/3PV4RZy6
Eu chequei isso
http://askubuntu.com/questions/82917/ubuntu-detects-only-3-2gb-ram-on-a-64bit-os
mas tenho certeza se pode ser o mesmo problema
Obrigado em avançado
Tente um kernel "pae"!
sudo apt-get install linux-generic-pae linux-headers-generic-pae