upgrading a ram for a laptop/pc, what to watch out for?

[initiald64]

What am i suppose to look out for when buying ram for Laptop/pc? would any ram will work as long as its a ddr3 or ddr2? or they must be the same such as SDRAM? would any make will work as long as it see fit? or clocking speed be crucial for this?
Reason i ask is cause i'm going to a computer market selling components and i though about my laptop and pc. Its a 64bits os i'm using for those who will ask.

 

[ldewitt]

Easy way to check is to use www.crucial.com use the system scanner to figure out what you can put in your laptop, it takes everything into effect OS, motherboard dimm slots and all that.

PS: I figured out what RAM i needed for my laptop using this site also.

 

[initiald64]

Yes i am aware of that but its much better to get warranty from shops as you dont have to send it and paying postage package. But then the market is much cheaper than those i see online. Of course those parts i found are genuine but i need the reminder as a guideline into buying it to meet the right specs.

 

[ldewitt]

Ah well everything comes into play here clock speeds, RAM SIZES. Ram functions better in pairs of the same speed/size. But if you have ddr3 ram 1gb 1600mhz and one ddr3 1gb 12800mhz they will both operate at the 1600mhz speed since it can only operate at the lowest speed of the 2.

You intern you can use different size sticks IE: 2x1GB with a 2Gb stick and it will be fine but it would perform faster with 4x1GB or 2x2GB.

I guess im not really knowing what your asking here and i assume from the lack of responses neither does anyone else.