Just how important is it that all your RAM be idnetical sticks.
I had 2GB of DDR RAM as 4 identical 512MB sticks, then 2 of these sticks failed in a spectacular crash. I sent them back to the firm that built the machine, who sent me two more...which failed immediately. So I sent them back again and asked them to send a pair they'd already tested. Unfortunately they sent me two sticks of a completely different make.
(Possibly because they couldn't find two sticks of the original make which did work. After all, 2 sticks failed while they were building the machine, 2 failed on me, then the two replacements failed. They claimed that 95% of this particular RAM had been problem free, which means that I somehow got the whole of the 5% that wasn't - or, that they were lying and the stuff is cheap crap.)
Anyway, my machine seems to be working. I haven't dared run MemTest yet, but preliminary boots seemed normal, Windows runs fine, etc. I'm just worried because I know it's recommended that all memory sticks be identical. I have arranged them in pairs - on my particular motherboard slots 1and 3, and 2 and 4 work together as pairs. Just how important is it that all 4 sticks should be identical?
I think it's ok to have different brands of ram in the same machine as long as the other specifications are the same. For example, if two of your 512 sticks are XYZ brand and the other two 512 sticks are ABC brand, your system should be fine if they are all PC2100 spec 266Mhz.
Basically, you want to have the speed of the ram sticks to be the same.
Well, I ´ve had problems before with different brands, and found out that there isn´t a rule to determine if it is going to work or not, even if they have the same specs. So, if you get the chance to have all of the same kind, do it, you certainly won´t regret. If you decide to stick with diferent brands, you will regret it or not.
Everything being equal (a big if), it _shouldn't_ matter what brand of memory you have as long as the specs are compatible. I've gotten burned on memory so many times that now I immediately run memtest86 (http://www.memtest86.com) on any machine that I put memory in. If memtest86 says things are ok, then you're good to go. If you want to aggressively tweak memory parameters in your BIOS, make sure you run memtest86 after each tweak to ensure you're still ok.
Memory must be absolutely perfect. If you have some bad memory somewhere, a program might write that memory region to disk, possibly corrupting program files over time. People whine about Windows being unstable, but perhaps 80% of the systems I've rebuilt because of 'Windows meltdowns' would not pass memtest86.
The PC powerup memory 'tests' are worthless. They just check to see if memory is sort of there. Likewise booting Windows doesn't tell you much- there could be problems in areas that Windows doesn't access until other programs run. The problem is even more actute with DAWs that have lots of memory.
I run memtest86 on my systems every few months. I've found that intermiittent bit errors sometimes develop over time with cheapo memory. Best to catch any memory problems before they spread like cancer.