Running amd64 but 8GB memory shows as 3349972 kB

I am running Debian testing and 'uname -a' shows:

3.13-1-amd64 #1 SMP Debian 3.13.7-1 (2014-03-25) x86_64 GNU/Linux

And 'dpkg --print-architecture' shows:

amd64

I have 4X2GB of ram installed and BIOS confirms this at 8192.

However, Linux sees only about 4.

'dmesg' shows:

Memory: 3334308K/3406004K available

And /proc/meminfo:

MemTotal: 3349972 kB

This is the output from 'dmidecode'

<SNIP>
Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x001FFFFFFFF
    Range Size: 8 GB
    Physical Array Handle: 0x0024
    Partition Width: 1

Handle 0x002A, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x0007FFFFFFF
    Range Size: 2 GB
    Physical Device Handle: 0x0025
    Memory Array Mapped Address Handle: 0x0029
    Partition Row Position: 1

Handle 0x002B, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00080000000
    Ending Address: 0x000FFFFFFFF
    Range Size: 2 GB
    Physical Device Handle: 0x0026
    Memory Array Mapped Address Handle: 0x0029
    Partition Row Position: 1

Handle 0x002C, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00100000000
    Ending Address: 0x0017FFFFFFF
    Range Size: 2 GB
    Physical Device Handle: 0x0027
    Memory Array Mapped Address Handle: 0x0029
    Partition Row Position: 1

Handle 0x002D, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00180000000
    Ending Address: 0x001FFFFFFFF
    Range Size: 2 GB
    Physical Device Handle: 0x0028
    Memory Array Mapped Address Handle: 0x0029
    Partition Row Position: 1

</SNIP>

Where to go from here?