I just bought a new pc and i had DDR400 256mb of ram. When i started the computer the memory frequency was 400. Now after adding DDR333 256mb ram, the memory frequency at startup has changed to 333. When i went to the bios i got a lot of options starting at i think 200 right up to about 600 and it was set at 333. What does this actually mean, can i take it up to the highest or not??

333MHz Ram is meant to run at 333MHz so there is not a chance it will ever reach 333MHz. If you're very lucky you may reach 400MHz but I doubt it. The reason for the settings up DDR600 is that you can buy 600MHz DDR Ram if you want to coerclock that system. That way you might be able to OC the FSB from 200 to 300MHz while running the Ram at 1:1 speed (DDR Ram alwasy counts double so with 300MHz you needed 600MHz Ram to run it at 1:1 Ratio). The important question for you is what's the original FSB of your CPU. If it has a basic setting of 200 (400)MHz your system might be faster with the 256MB at 400MHz instead of the 512MB running at 333MHz. Better check that with some benchmark programs you can download from the net. If it's 166 (333)MHz instead the 512MB at 333MHz might be faster. The reason behind this is that at 1:1 Ratio cpu and ram work at the same clock rate. With any other ratio they have to wait on each other again and again and in that time they can not work. It just depends on the speed difference. For example with old SD Ram there was only 100MHz or 133MHz (the old 66MHz system I don't count here) so if you raised the ram speed it worked 33% faster. That was still faster than the loss of waiting time compared to a 100MHz FSB. With the step from 166 to 200MHz this is no longer true. Here the additional ram size comes into account so it's difficult which would be faster!

Basically, the motherboard will autodetect the RAM, then adjust the settings so that BOTH sticks of RAM run at the speed of the slowest stick. Since you installed PC2700 (DDR333) with PC3200 (DDR400), both will run as PC2700. If you had installed PC2100 (DDR266) with PC3200, both would run as PC2100. You may be able to "force" the lower rated RAM stick to run at the speed of the higher rated stick by manually adjusting the RAM settings in the BIOS, but chances are, your PC2700 won't be capable of running as PC3200. Knowing the make/model of your board & what CPU you have would be helpful. As Free Weasel mentioned, for best performance you should strive to run your CPU & RAM at a 1:1 ratio. And there's also dual channel mode to consider. ASUS A7N8X-X Athlon XP 1800+ 8.5 x 200MHz 1024MB PC3200 2.5-3-3-7 Asus A9550GE/TD 128MB WinME/WinXP Pro SP2

To answer Weasel's question, i have a 2.8ghz CPU and the FSB is i think 200mhz. In the bios i have an option to adjust the FSB between 200 and 355mhz, it's 478 compatible cpu with HTT. Anyway i understand what Jam is saying because a friend of mine that i took the ram from has a 400mhz ram and when he put these two together his pc became VERY slow that's why he gave it to me, but now that i know i think i'll go back to the 256. However, i increased the memory frequency at the bios to 400mhz and it's still running, is it save??. Go to the link below and check out my specs!! http://img478.imageshack.us/img478/8250/motherboard5lu.jpg

It doesnt matter what you do to the BIOS the RAM will crash, think of instructions and fequecny like kids flicking a light switch. Sure the light bulb will turn on and off really fast, but in 20 to 30 seconds its gona burn out. Chips are made of small transistors, PNP or 101 or on off on - if it cant handle 101 at that speed its eventualy going to give up. WinXP PRO SP2 ASUS AN78X-X BIOS ASUS 1014 beta 2 PC3200 768 1.5t 3t 3t 6t AMD XP 2600+ @ 2.2 ATI AIW 9800 PRO

If i increase the memory frequency too high does that mean that my pc will shutdown or is my ram going to be damaged??