Type sudo lshw to your favourite terminal for comprehensive list of your hardware, including info about your RAM.
root@ubuntumike:~# sudo lshw
ubuntumike
description: Desktop Computer
product: To Be Filled By O.E.M.
vendor: To Be Filled By O.E.M.
version: To Be Filled By O.E.M.
serial: To Be Filled By O.E.M.
width: 32 bits
capabilities: smbios-2.4 dmi-2.4 smp-1.1 smp
configuration: boot=normal chassis=desktop cpus=2 uuid=00020003-0004-0005-0006-000700080009
*-core
description: Motherboard
product: ALiveXFire-eSATA2
vendor: ASRock
physical id: 0
*-firmware
description: BIOS
vendor: American Megatrends Inc.
physical id: 0
version: P3.10 (02/16/2009)
size: 64KiB
capacity: 448KiB
capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb ls120boot zipboot biosbootspecification
*-cpu:0
description: CPU
product: AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
vendor: Advanced Micro Devices [AMD]
physical id: 4
bus info: cpu@0
version: 15.11.2
serial: To Be Filled By O.E.M.
slot: CPUSocket
size: 2231MHz
width: 64 bits
clock: 200MHz
