Advice needed on RAM configuration

I am upgrading the RAM on my two PC's and was just wondering what would be the best way to do it.

My main PC is a Dell XPS 420 with dual E8500 processors running Windows 8 64bit, dual channel is available on the motherboard. I currently have 3 x 1gb of RAM and one slot available out of four. Should I just add a 1gb stick so that they are all the same? or add a 2gb stick and run with 5gb all together? or add a 2gb stick and remove a 1gb stick and run with 4gb in 3 slots and then buy another 2gb stick when I have more cash?

The second PC is an old Dell Dimension 3000 with a Pentium 4 running Crunchbang 32 bit, no dual channel on motherboard as far as I can tell. I currently have 256mb RAM sticks installed in the two available slots and I've just bought a 1gb stick. Should I just run with the 1gb on its own or with a 256mb stick in the other slot?

 

The Dell XPS 420 maxes out at DDR2 PC2-6400 2gigs X 4 sticks.

The Dell Dimension 3000 maxes out at DDR1 PC-3200 1gig X 2 sticks.

Both are dual channel.

http://ark.intel.com/products/27708/Intel-82865GV-Graphics-and-Memory-Controller

^That is your Dell Dimension 3000 chipset^

For best performance you can max out to these specs but as ram amount trumps ram speed, installing as much as you can regardless of speed and matching type will likely be an acceptable choice. Hard drives on these older systems is the major bottleneck so lots of ram helps keep the disk swapping to minimum and things running smoothly.

 

Sticking with decent brands this is the cheapest you can go if you wanted to truly max out:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231039

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231207 * 2

You could go a little faster with tighter latencies but there is no way to justify the price jump on systems this old.

 

Based on your advice I am running with as much RAM as possible in the Dimension 3000 (1.2gb) and it is working well. I will do the same with the XPS 420 and increase by 2gb at a time when I can afford it.

Thanks for the info.