if you have 4 ram slots do you need exacly 4 ram sticks?

Solution
do not guess , check in the motherboard manual

they have to tell you how to install your memory to be in dual channel , you can put 2 or 4 memory in dual channel usually

Rune Olsen

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Mar 27, 2013
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No you don't need 4 ram sticks. 2 and 2 is perfectly fine. I have no idea what motherboard you have tho, so i just assume it is Dual-Channel. If you decide to use 2 sticks you'll have to put em in either slot 1 and 3 or 2 and 4.
Just make sure the sticks are the same size
 
If the are dual channel, the slots will be paired in two different colours. If the aren't, you can put in one, two or three sticks if you can't find four but if they are different colours, each pair of sticks have to match each other exactly so it's either two or four - nothing in between.
 
The photograph I saw when I Googled it up appeared to my ageing eyesight to have four slots the same colour. Sorry if I'm wrong but that's my best excuse. Apart from that, the description showed the same RAM spec for all four slots. Where did you see dual-channel?
 
You need four slots for dual-channel - as I said in my earlier posts two will be a different colour but when I looked at the photogragh I found on Google (the same one to which you later linked) what I saw was definitely misleading. All the dual-channel boards I've seen have had different colours for the dual pair from the base pair.

Either way, 32Gb is huge and you can match all four sticks for maximum benefit or just two then add two later if you want to.