"Now it is: 4 Barc cores will outperform 2 K8 cores by up to 40 to 70%. Big deal."

Those are handpicked benches. One is the outdated SPECfp_rate2000
http://i17.tinypic.com/2eq51k5.jpg and the other "OLTP" (usually they should specify if this is TPC-C or H) http://i16.tinypic.com/4d6wjmo.jpg

http://online.wsj.com/article/SB1183...googlenews_wsj
http://news.moneycentral.msn.com/pro...629&ID=7108474
http://www.channelregister.co.uk/200...arcelona_2ghz/
"Mr. Allen estimated that the first versions of Barcelona still will be 40% to 50% faster than existing Opteron chips, which have two processors."
"We will be seeing a performance boost of 40-50 per cent above our highest frequency dual-core products that are available today," AMD VP Randy Allen told us.

Some calculating, the fastest 2P K8 can deliver 4*3GHz=12GHz. 45% (40+50/2) faster than that would be 17.4Ghz. Divided by 8 K10 cores=2.175GHz. 2.175/2=8.75% IPC K10 advantage?