Among the different chipset series motherboard
Which chipset suppot 2400mhz
I want an i7 4790k
Is it true that u must have a 2400mhz ram for an i7 4790k?
Can I have same performance with 1600mhz?
"Is it true that u must have a 2400mhz ram for an i7 4790k?" - no. You can have from 1066MHz up
eg ASRock Z96 Extreme 6 - http://www.asrock.com/mb/Intel/Z97%20Extreme6/?cat=Specifications - "Supports DDR3 3200+(OC)/2933(OC)/2800(OC)/2400(OC)/2133(OC)/1866(OC)/1600/1333/1066 " - so from 1066 to 3200 - all are good. I recommend 2 x 4 gb 1866 cas 9 1.5v ram eg Mushkin Redline, GSkill Ares or Sniper.
"Is it true that u must have a 2400mhz ram for an i7 4790k?" - no. You can have from 1066MHz up
eg ASRock Z96 Extreme 6 - http://www.asrock.com/mb/Intel/Z97%20Extreme6/?cat=Specifications - "Supports DDR3 3200+(OC)/2933(OC)/2800(OC)/2400(OC)/2133(OC)/1866(OC)/1600/1333/1066 " - so from 1066 to 3200 - all are good. I recommend 2 x 4 gb 1866 cas 9 1.5v ram eg Mushkin Redline, GSkill Ares or Sniper.