A type of multi-core technology that includes two separate dual-core dies, where dual-core means a CPU that includes two complete execution cores per physical processor, installed together in one CPU package. In this set-up cores 1 and 2 would share a memory cache, as would cores 3 and 4. If core 1 or 2 needs to communicate with 3 or 4, it is an external communication, usually via the frontside bus. Both Intel and AMD have introduced quad-core processors, starting with Intel in late 2006.