Why the Xbox 720 and PS4 will have a RAM of 4 GB

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Salnax said:

Generation	Nintendo	Sega	Sony	Microsoft	Average
3	4.5 KB	24 KB	N/A	N/A	14 KB
4	256 KB	136 KB	N/A	N/A	196 KB
5	4 MB	5 MB	3.5 MB	N/A	4.2 MB
6	43 MB	26 MB	38 MB	64 MB	43 MB
7	91 MB	N/A	512 MB	522 MB	375 MB
8	2 GB	N/A	N/A	N/A	N/A

The pattern is simplier than you suggest and the Wii to WiiU jump is just as modest as it was previously.

Its roughly a 10x jump in each iteration with the exception of Nintendo, which has moved to a 2x jump. Since both MSony were near .5GB then they will be around 5GB as a best case argument. But i don't think its as linear as this suggests; PS2 to PS3 was larger than 10x.

While I contend the systems will use 4GB as that makes the most logical sense, the rumors currently suggest closer to 6GB as the dev kits have had 8GB reportedly.