Importance of Matching RAM?

In the grand scheme of things, how important is "matching" RAM?

I mean, I have the same "numbers" on all four of these sticks (I think?), but they're different "brands" (1GB is whatever the 2 sticks of 512 that Dell sent me from the factory, and the other 2GB is the PNY that I bought separately).

Obviously if I was going to upgrade, I'd get rid of the 2 Dell sticks of 512 ... but if I was to do it "incrementally", would it benefit me (much) to get 1GB of PNY now, to replace the two 512's (for awhile), until I can afford another 1 GB stick of PNY, or should I just wait until I can get (afford) two more 1GB sticks of PNY? Or again, does it matter about brands, as long as all the numbers are the same/match?

I've read (a time or two) that this machine is (most machines are) only going to "recognize" 3 to 3 & 1/2 GB of RAM (MAX) anyway (for some reason or other?).

Thanks in advance,
g...
PS ~ am I making ANY sense here whatsoever ... please??

 

Keep your money in your pocket as 'upgrading' will not give you much, if any, improvement that you would notice. The matched RAM is for dual/triple-channel for extra performance. As to max usable RAM, it's either you have a 32-bit CPU and can only run a 32-bit OS or have a 64-bit CPU but only have a 32-bit OS. The 64-bit OS's can handle up to 128GB RAM. Since everything is working nicely then don't 'fix' it.

 

Well thanks, but that's just the point...this machine has rarely (if ever) worked "nicely".

I don't know if it's the junk Vista OS, or what exactly, but, well ... now that I think about it I have "issues" with both machines (the other machine is XP) - and, come to think of it, BOTH have mismatched (brand-wise) RAM.

 

Easy enough to find out, pull the new mismatched RAM out, and see how things work, One thing to make sure is that the RAM is on the motherboard's QVL(qualified vendour list).

 

Pretty sure that all the RAM is qualified...I have the original Dell stuff, what I bought from Crucial, and some PNY (between the two machines).