I gonna buy 184-pin DIMM socket, unbuffered, non-ECC 400MHz DDR SDRAM mem mod. Could you tell the RAM speed, and the bus speed ? Can I use no-problemly 3 RAM from diff manufac. in a main board?

Depending on the chipset or memory controller. It is best to have all RAM from the same manufacture, but it can be mix and match with some reliability and stability problems. The speed of each memory can be a different speed, but the slowest memory will make the faster memory be as slow as the slowest memory. Some chipset models have dual-channel memory, so the rules of the same brand and as well the model have to be the same for the best reliability and stability.

The RAM speed is what ever the chipset or memory controller is clocked at. The RAM speed for a 400 MHz clock should be 433 MHz. The reason for a selection of higher speed memory is because of different quality during manufacturing, the regulation of power supply for the memory, and heat. The RAM speed relates to the accessing time. The spec for 433 MHz or a JEDEC spec of PC3500 should have an accessing time of 2.3 nanosecond (ns). To calculate the RAM speed in MHz to time, convert MHz to hertz and plug it in an inverse equation. For a 433 MHz (433000000), 1/433000000 = 2.309 X 10^-9 or 2.309 ns. You can do the same for 400 MHz, but it should be around 2.5 ns.

http://www.linuxquestions.org/questi...light=ram+tute Here is another thread asking about ram, where I gave a very detailed look into ram, and exactly what kind to get given the situation and hardware you currently have.