Saya menjalankan Debian Squeeze (x64):
# uname -srvmo
Linux 2.6.32-5-amd64 #1 SMP Mon Jan 16 16:22:28 UTC 2012 x86_64 GNU/Linux
Saya memiliki 2 stick DDR2 2 GB yang kompatibel di motherboard G31M-S saya . Ini mendukung hingga 8GB:
Karena ini adalah server, saya tidak terlalu peduli dengan grafis. Jadi saya mengaturnya ke yang terendah.
Internal Graphics Mode Select: Auto
Enabled, 1MB <--
Enabled, 8MB
DVMT Mode Select: Fixed Mode <--
Auto
DVMT/FIXED Memory: 128MB <--
256MB
Namun, Linux hanya mendeteksi memori 3,19GiB:
# cat /proc/meminfo
MemTotal: 3350712 kB
...
Melihat peta E820 :
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
[ 0.000000] BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
[ 0.000000] BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved)
[ 0.000000] BIOS-e820: 0000000000100000 - 00000000cfdb0000 (usable)
[ 0.000000] BIOS-e820: 00000000cfdb0000 - 00000000cfdc0000 (ACPI data)
[ 0.000000] BIOS-e820: 00000000cfdc0000 - 00000000cfdf0000 (ACPI NVS)
[ 0.000000] BIOS-e820: 00000000cfdf0000 - 00000000cfe00000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
[ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
[ 0.000000] BIOS-e820: 00000000ff380000 - 0000000100000000 (reserved)
[ 0.000000] DMI present.
[ 0.000000] AMI BIOS detected: BIOS may corrupt low RAM, working around it.
[ 0.000000] e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved)
Dan melakukan sedikit matematika:
>>> ((0x9F800 - 0x10000) + (0xCF6B0000 - 0x100000)) / 1024.0 / 1024.0 / 1024.0
3.240476608276367
Kami mendapatkan jawaban yang hampir sama.
Apa yang saya lewatkan?
Saya tidak sepenuhnya membeli argumen "ruang alamat PCI". Mengambil salah satu dari dua 2GB yang menonjol, layar pengaturan menunjukkan 2048MB.
# cat /proc/meminfo
MemTotal: 2058432 kB
Itu 1.96GB.
Peta E820 lagi:
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
[ 0.000000] BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
[ 0.000000] BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved)
[ 0.000000] BIOS-e820: 0000000000100000 - 000000007fdb0000 (usable)
[ 0.000000] BIOS-e820: 000000007fdb0000 - 000000007fdc0000 (ACPI data)
[ 0.000000] BIOS-e820: 000000007fdc0000 - 000000007fdf0000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000007fdf0000 - 000000007fe00000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
[ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
[ 0.000000] BIOS-e820: 00000000ff380000 - 0000000100000000 (reserved)
[ 0.000000] DMI present.
[ 0.000000] AMI BIOS detected: BIOS may corrupt low RAM, working around it.
[ 0.000000] e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved)
Dan matematika ...
>>> ((0x9F800 - 0x10000) + (0x7fdb0000 - 0x100000)) / 1024.0 / 1024.0 / 1024.0
1.9973125457763672
Jadi saya mendapat 2GB / 2GB. /proc/cpuinfo
menunjukkan bahwa prosesor saya mendukung pengalamatan fisik 36-bit. 2 ^ 36 = 64GB, yang saya bahkan tidak dekat.
# ./smem -R 4G -w
Area Used Cache Noncache
firmware/hardware 843592 0 843592
kernel image 0 0 0
kernel dynamic memory 181116 134616 46500
userspace memory 287784 19736 268048
free memory 2881812 2881812 0