Part of the unique requirements of RIMM memory is that it must be used in pairs of the same brand, size, and specs. Two RIMM's of differing type will not work, nor will a single RIMM module. As if that wasn't enough to remember, there can be no empty RIMM slots on the motherboard either.

CRIMM spacer module. Needed if any unused RIMM module slots.

Does that mean you'll have to buy all the memory needed to completely fill the each memory slot? Thankfully no it doesn't. Motherboard manufacturers should include two CRIMM spacer modules that can be inserted into the two empty memory slots if they are unused.

Component No.4: RIMM memory (x2)
Example: Samsung PC800 RIMM

The Pentium 4 is known for its endless obsession with power, both in terms of speed and electricity. For the person facing the upgrade to a build-your-own P4 system, a new power supply is a must unfortunately.