http://support.apple.com/kb/SP576 Scroll down to Configurations. The Frontside bus for the Core 2 Duo 21.5-inch and 27-inch lists the Frontside bus as 1066Mhz. The Frontside Bus for the the Core i5 is listed as - . The Memory for Lynnfield chips; which the new iMac Quad-Core uses is 1333mhz. http://en.wikipedia.org/wiki/List_of_Intel_Core_i7_microprocessors#.22Lynnfield.22_.2845_nm.29 Will buying these http://www.newegg.com/Product/Product.aspx?Item=N82E16820231295 over these http://www.newegg.com/Product/Product.aspx?Item=N82E16820231294 create less of a bottleneck? P.S. Is anyone thinking about putting in a WD Velociraptor in there new iMacs?