我安装了两张 4GB = 8GB RAM 的内存卡，而 Ubuntu 14.04 LTS 64 位只显示 4GB RAM。我怎样才能让它显示整个 8GB？
您可以在下面看到详细信息，我还提供了一些图形（ATI Mobility Radeon HD 5650）信息，以防它占用了 RAM 内存。
顺便说一下，这是一台 HP Pavilion dv7-4012eg，配备 Intel(R) Core(TM) i7 CPU Q 720 @ 1.60GHz。
jessy@linx:~$ free -m
total used free shared buffers cached
Mem: 3887 1850 2036 3 285 745
-/+ buffers/cache: 819 3067
Swap: 8192 0 8192
jessy@linx:~$ sudo dmidecode -t 17
[sudo] password for jessy:
# dmidecode 2.12
SMBIOS 2.6 present.
Handle 0x0018, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x0017
Error Information Handle: 0x0019
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: SODIMM
Set: None
Locator: Bottom - Slot 1
Bank Locator: BANK 0
Type: DDR3
Type Detail: Synchronous
Speed: 1333 MHz
Manufacturer: Samsung
Serial Number: 977A35A0
Asset Tag: Unknown
Part Number: M471B5173BH0-CK0
Rank: 1
Handle 0x001B, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x0017
Error Information Handle: 0x001C
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: SODIMM
Set: None
Locator: Bottom - Slot 2
Bank Locator: BANK 1
Type: DDR3
Type Detail: Synchronous
Speed: 1333 MHz
Manufacturer: Nanya
Serial Number: 0676036D
Asset Tag: Unknown
Part Number: M2S4G64CB8HG5N-DI
Rank: 2
jessy@linx:~$ sudo lshw -c memory
*-firmware
description: BIOS
vendor: Hewlett-Packard
physical id: 0
version: F.29
date: 11/07/2011
size: 1MiB
capacity: 1472KiB
capabilities: pci upgrade shadowing cdboot bootselect edd int13floppynec int13floppytoshiba int13floppy360 int13floppy1200 int13floppy720 int13floppy2880 int9keyboard int10video acpi usb biosbootspecification
*-cache:0
description: L3 cache
physical id: 13
slot: L3 Cache
size: 6MiB
capacity: 6MiB
capabilities: synchronous internal write-through unified
*-cache:1
description: L2 cache
physical id: 15
slot: L2 Cache
size: 256KiB
capacity: 256KiB
capabilities: synchronous internal write-through unified
*-cache:2
description: L1 cache
physical id: 16
slot: L1 Cache
size: 32KiB
capacity: 32KiB
capabilities: synchronous internal write-through instruction
*-cache
description: L1 cache
physical id: 14
slot: L1 Cache
size: 32KiB
capacity: 32KiB
capabilities: synchronous internal write-through data
*-memory
description: System Memory
physical id: 17
slot: System board or motherboard
size: 8GiB
*-bank:0
description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns)
product: M471B5173BH0-CK0
vendor: Samsung
physical id: 0
serial: 977A35A0
slot: Bottom - Slot 1
size: 4GiB
width: 64 bits
clock: 1333MHz (0.8ns)
*-bank:1
description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns)
product: M2S4G64CB8HG5N-DI
vendor: Nanya
physical id: 1
serial: 0676036D
slot: Bottom - Slot 2
size: 4GiB
width: 64 bits
clock: 1333MHz (0.8ns)
jessy@linx:~$ dmesg | grep e820
[ 0.000000] e820: BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009cfff] usable
[ 0.000000] BIOS-e820: [mem 0x000000000009d000-0x000000000009ffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bbe3efff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000bbe3f000-0x00000000bbebefff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bbebf000-0x00000000bbfbefff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bbfbf000-0x00000000bbffefff] ACPI data
[ 0.000000] BIOS-e820: [mem 0x00000000bbfff000-0x00000000bbffffff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000bc000000-0x00000000bfffffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000f0000000-0x00000000f7ffffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000feb00000-0x00000000feb03fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000fed10000-0x00000000fed13fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000fed18000-0x00000000fed19fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000fed1b000-0x00000000fed1ffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000ffe80000-0x00000000ffffffff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000013fffffff] usable
[ 0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
[ 0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
[ 0.000000] e820: last_pfn = 0x140000 max_arch_pfn = 0x400000000
[ 0.000000] e820: last_pfn = 0xbc000 max_arch_pfn = 0x400000000
[ 0.000000] e820: [mem 0xc0000000-0xefffffff] available for PCI devices
[ 1.215263] e820: reserve RAM buffer [mem 0x0009d000-0x0009ffff]
[ 1.215265] e820: reserve RAM buffer [mem 0xbbe3f000-0xbbffffff]
jessy@linx:~$ sudo dmesg | grep drm
[sudo] password for jessy:
[ 19.533784] [drm] Initialized drm 1.1.0 20060810
[ 19.595888] [drm] radeon kernel modesetting enabled.
[ 19.596328] [drm] initializing kernel modesetting (REDWOOD 0x1002:0x68C1 0x103C:0x1449).
[ 19.596370] [drm] register mmio base: 0xD4000000
[ 19.596373] [drm] register mmio size: 131072
[ 19.596610] [drm] Detected VRAM RAM=1024M, BAR=256M
[ 19.596613] [drm] RAM width 128bits DDR
[ 19.598366] [drm] radeon: 1024M of VRAM memory ready
[ 19.598369] [drm] radeon: 1024M of GTT memory ready.
[ 19.598443] [drm] Loading REDWOOD Microcode
[ 20.529509] [drm] GART: num cpu pages 262144, num gpu pages 262144
[ 20.531705] [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[ 20.551741] [drm] PCIE GART of 1024M enabled (table at 0x000000000025D000).
[ 20.553301] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 20.553302] [drm] Driver supports precise vblank timestamp query.
[ 20.553386] [drm] radeon: irq initialized.
[ 20.570449] [drm] ring test on 0 succeeded in 2 usecs
[ 20.570464] [drm] ring test on 3 succeeded in 6 usecs
[ 20.756575] [drm] ring test on 5 succeeded in 2 usecs
[ 20.756588] [drm] UVD initialized successfully.
[ 20.756969] [drm] Enabling audio 0 support
[ 20.757033] [drm] ib test on ring 0 succeeded in 0 usecs
[ 20.757091] [drm] ib test on ring 3 succeeded in 0 usecs
[ 20.908562] [drm] ib test on ring 5 succeeded
[ 20.965712] [drm] radeon atom DIG backlight initialized
[ 20.965717] [drm] Radeon Display Connectors
[ 20.965720] [drm] Connector 0:
[ 20.965722] [drm] LVDS-1
[ 20.965725] [drm] DDC: 0x6560 0x6560 0x6564 0x6564 0x6568 0x6568 0x656c 0x656c
[ 20.965726] [drm] Encoders:
[ 20.965728] [drm] LCD1: INTERNAL_UNIPHY
[ 20.965730] [drm] Connector 1:
[ 20.965731] [drm] HDMI-A-1
[ 20.965733] [drm] HPD1
[ 20.965735] [drm] DDC: 0x6430 0x6430 0x6434 0x6434 0x6438 0x6438 0x643c 0x643c
[ 20.965737] [drm] Encoders:
[ 20.965738] [drm] DFP1: INTERNAL_UNIPHY1
[ 20.965740] [drm] Connector 2:
[ 20.965741] [drm] VGA-1
[ 20.965744] [drm] DDC: 0x64d8 0x64d8 0x64dc 0x64dc 0x64e0 0x64e0 0x64e4 0x64e4
[ 20.965745] [drm] Encoders:
[ 20.965747] [drm] CRT1: INTERNAL_KLDSCP_DAC1
[ 20.965825] [drm] Internal thermal controller without fan control
[ 21.029449] [drm] radeon: dpm initialized
[ 21.889804] [drm] fb mappable at 0xC045E000
[ 21.889808] [drm] vram apper at 0xC0000000
[ 21.889810] [drm] size 5787648
[ 21.889812] [drm] fb depth is 24
[ 21.889814] [drm] pitch is 6400
[ 21.890122] fbcon: radeondrmfb (fb0) is primary device
[ 23.808455] radeon 0000:01:00.0: fb0: radeondrmfb frame buffer device
[ 23.808578] [drm] Initialized radeon 2.36.0 20080528 for 0000:01:00.0 on minor 0
[ 61.998447] Modules linked in: rfcomm bnep bluetooth nls_utf8 cifs fscache snd_hda_codec_hdmi uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core videodev hp_wmi sparse_keymap arc4 snd_hda_codec_idt coretemp snd_hda_intel snd_hda_codec snd_hwdep ath9k kvm snd_pcm ath9k_common ath9k_hw snd_page_alloc snd_seq_midi ath snd_seq_midi_event radeon snd_rawmidi mac80211 joydev serio_raw i7core_edac edac_core cfg80211 snd_seq ttm snd_seq_device drm_kms_helper snd_timer lpc_ich mei_me drm mei snd soundcore i2c_algo_bit wmi hp_accel lis3lv02d video input_polldev mac_hid parport_pc ppdev lp parport ahci psmouse r8169 libahci mii
jessy@linx:~$ file /sbin/init
/sbin/init: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=7a4c688d009fc1f06ffc692f5f42ab09e68582b2, stripped
jessy@linx:~$ uname -a
Linux linx 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
jessy@linx:~$ cat /proc/meminfo
MemTotal: 3980292 kB
MemFree: 215584 kB
Buffers: 266516 kB
Cached: 962476 kB
SwapCached: 12 kB
Active: 2545688 kB
Inactive: 879940 kB
Active(anon): 1943544 kB
Inactive(anon): 278912 kB
Active(file): 602144 kB
Inactive(file): 601028 kB
Unevictable: 724 kB
Mlocked: 724 kB
SwapTotal: 8389596 kB
SwapFree: 8388180 kB
Dirty: 152 kB
Writeback: 0 kB
AnonPages: 2197400 kB
Mapped: 294696 kB
Shmem: 25820 kB
Slab: 205660 kB
SReclaimable: 88652 kB
SUnreclaim: 117008 kB
KernelStack: 6208 kB
PageTables: 52164 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 10379740 kB
Committed_AS: 7787880 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 161204 kB
VmallocChunk: 34359566624 kB
HardwareCorrupted: 0 kB
AnonHugePages: 407552 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 84224 kB
DirectMap2M: 4042752 kB
jessy@linx:~$ sudo dmidecode --type memory
[sudo] password for jessy:
# dmidecode 2.12
SMBIOS 2.6 present.
Handle 0x0017, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 8 GB
Error Information Handle: No Error
Number Of Devices: 2
Handle 0x0018, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x0017
Error Information Handle: 0x0019
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: SODIMM
Set: None
Locator: Bottom - Slot 1
Bank Locator: BANK 0
Type: DDR3
Type Detail: Synchronous
Speed: 1333 MHz
Manufacturer: Samsung
Serial Number: 977A35A0
Asset Tag: Unknown
Part Number: M471B5173BH0-CK0
Rank: 1
Handle 0x001B, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x0017
Error Information Handle: 0x001C
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: SODIMM
Set: None
Locator: Bottom - Slot 2
Bank Locator: BANK 1
Type: DDR3
Type Detail: Synchronous
Speed: 1333 MHz
Manufacturer: Nanya
Serial Number: 0676036D
Asset Tag: Unknown
Part Number: M2S4G64CB8HG5N-DI
Rank: 2
jessy@linx:~$ sudo dmesg | grep "Memory"
[ 0.000000] Memory: 3958676K/4126576K available (7383K kernel code, 1144K rwdata, 3408K rodata, 1336K init, 1444K bss, 167900K reserved)
[ 61.998446] Memory corruption detected in low memory
答案1
插槽 2 中的内存芯片可能有缺陷，但我不这么认为。尝试交换两个芯片，以便 Nanya 芯片位于插槽 1。由于它们不同，它们可能具有不同的时序（我们人类无法察觉），但 BIOS 会认为另一个芯片已关闭。交换它们将使 BIOS 通过 Nanya 芯片（两者中较小的一个）设置其参数，并且它应该可以工作。