Question 1

will it fit in a pci X16?

Accepted Answer

It should work with any pci-e x16 slot, the version should not matter

Question 2

my system got 255w soo i can use it ?

Accepted Answer

It is impossible to answer that question without knowing the draw of all the other components in the system, but I would hesitate to put any gaming card in a system with wattage that low. 400W is the minimum for a baseline gaming system these days. Better to have more than you need. Remember, every component in your system is drawing wattage from the PSU. Add up the draw of all of them, and then give yourself a nice buffer of at least 50 watts, preferably 100.

Question 3

can i able to run high graphics games like watch dog,titanfall,assassin's creed unity,shadow of mordor etc on this video card...?

Accepted Answer

That depends on your setup and what you expect - more likely than not you can run them in a lower resolution on a single monitor, but a multi-monitor setup or full graphics is out of the question.  The biggest problem stems from Gigabyte's decision to not allow Crossfire; what might be possible in other R7 240 setups with Crossfire support isn't possible at all with this particular card.

Question 4

Why is this card so cheap compared to the other R7 240?

Accepted Answer

From the Specifications tab.
8.5" x 5.1" x 1.5"

Questions & Answers