Registered vs. Unregistered DDR RAM - What is it?

by billv - 11/1/04 7:02 AM

I recently purchased a refurbished Dell 4600 PC that I intend to use as a video editing station. It's a 3.06 GHz P4 system with 800 MHz Hyperthreading FSB. It came loaded with 1 GB of PC2700 333MHz DDR RAM in two 512MB 184-pin DIMMs (non-parity, non-ECC, unbuffered), which (according to the manual) run at 320MHz. If I understand this correctly, the FSB runs at the 533MHz clock rate instead of the rated 800MHz because of the slower RAM that's installed. There are also 2 empty DIMM slots on the motherboard.

I'm looking at trying to upgrade the memory in this system to either 2 or 4 GB of PC3200 400MHz DDR dual channel RAM to increase performance. When I looked on eBay and, I saw PC3200 DDR RAM advertised as either "registered" or "unregistered" and "low density" or "high density". What the heck does that mean when I'm trying to find memory compatible with my motherboard?

Also, if anyone has any recommendations as to what brand of DDR RAM I should buy, I would appreciate hearing from you. Corsair, Kingston, and OCZ brands are some I've seen advertised.

Thanks, Bill V