determine hardware configuration using command line

dmidecode will tell you how the RAM etc. reports itself, by decoding information in a table. There's an Ubuntu package of it already too. The relevant parts of an example output might be:

Handle 0x0005, DMI type 5, 22 bytes
Memory Controller Information
    Error Detecting Method: 64-bit ECC
    Error Correcting Capabilities:
        None
    Supported Interleave: One-way Interleave
    Current Interleave: One-way Interleave
    Maximum Memory Module Size: 1024 MB
    Maximum Total Memory Size: 3072 MB
    Supported Speeds:
        Other
    Supported Memory Types:
        Other
        DIMM
        SDRAM
    Memory Module Voltage: 3.3 V
    Associated Memory Slots: 3
        0x0006
        0x0007
        0x0008
    Enabled Error Correcting Capabilities:
        Unknown

Handle 0x0006, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM 1
    Bank Connections: 0 1
    Current Speed: Unknown
    Type: Other DIMM SDRAM
    Installed Size: 256 MB (Double-bank Connection)
    Enabled Size: 256 MB (Double-bank Connection)
    Error Status: OK

Be careful though, some BIOS implementations are faulty and/or outright lie in this data.

A tool named

 lshw

can tell exactly what you need.

It actually uses dmidecode for the memory, but provides more information about the hardware in overall.

There are enough quirks (for example, in 18-bank HP xeon motherboards, you can only use 12 for unbuffered memory) that your best bet is really to find out the board and ask the manufacturer. For example, HP has a memory configuration website. Dmidecode and other software solutions don't tell the full story. Not even the BIOS can tell yo all of the pitfalls.