dunno if this was already posted but the 512mb version stock mem speed is 1800mhz and the 256mb version stock mem speed is 1400mhz
http://www.nvidia.com/page/geforce8.html
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150264
http://www.nvidia.com/page/geforce8.html
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150264