http://www.eetimes.com/document.asp?doc_id=1141534
Somewhat hilariously Intel released "Coppermine" series of CPUs in 1999, but those used Alu interconnects :D and were famously unstable above 1GHz.
AMD was also first to 1GHz. http://www.anandtech.com/show/498/4
Intel was even trying to dispute that fact, but its hard to convince PC hardware journalists you are first when they are already testing 1GHz Athlons on their own desks while reading Intel press release about closed door demonstration.
http://www.zdnet.com/article/1-ghz-intel-claims-it-was-first...