Checking which memory banks are used on Linux

Today, I decided that I want to upgrade from 2 GB to 4 BG memory on my laptop. However, I didn't know how this memory was distributed - was it two 1GB chips, or a single 2 GB chip? Luckily, a colleague of mine found this command:

sudo lshw -c memory

which, among other things, produced these lines:

*-memory
description: System Memory
physical id: 2b
slot: System board or motherboard
size: 2GiB
*-bank:0
description: SODIMM DDR2 Synchronous 667 MHz (1.5 ns)
physical id: 0
slot: DIMM 1
size: 2GiB
width: 64 bits
clock: 667MHz (1.5ns)
*-bank:1
description: SODIMM DDR2 Synchronous 667 MHz (1.5 ns) [empty]
physical id: 1
slot: DIMM 2
clock: 667MHz (1.5ns)

Voila! From this info it's easy to see that memory bank 1 has 2 GB of memory, and bank 2 is empty.