I have a corsair vengeance 8gig DDR3 RAM in one slot. I want to upgrade it with same speed and capacity but with other brand. Does they work fine? Or I have to use the same brand? TIA
Most likely yes....
- if the specs for the RAM are the same - size, speed & timings
- if the motherboard supports both sticks
If you have problems, you may be able to mitigate it by tweaking BIOS settings, but many motherboards will compensate for minor discrepancies (ie. lowering timings). You should be fine to trial it - you are not going to break anything. In fact, it will most likely work initially, but you will find the issue will be stability under load.
However, you are unlikely to be able to get support if you have any issues for OEMs - they will likely insist you do not mix & match, and will probably recommend Matched Pairs (sets of sticks that have been tested to work well together).