For many years, multiprocessor systems were things you saw only at businesses, where the demand for processing power outweighed the costs involved. Starting in the late 90s, home users started to see a drop in price of boards offering SMP to where it would make sense for someone who had a CPU-intensive hobby to buy a dual processor board, such as the infamouns ABIT BP6 or the Tyan Tiger MPX. It wasn't until the advent of dual-core desktop processors, however, that SMP has truly been able to embrace the home environment completely, with a cost that is only marginally more than a single core variant. AMD and Intel both seek to push that even farther, and as such AMD has changed their minds and decided that soon they will have an enthusiast platform called "4x4" that will let you use dual mutli-core CPUs in one machine. Essentially, a desktop would have the power of a quad-CPU powerhouse. It gets even better, with potential plans from both AMD and Intel to incorporate 4 cores onto one die, and perhaps even more in the future. All of this cool stuff isn't that far off, either:

"The 4x4 platform will be designed to be upgraded to eight total processor cores when AMD launches quad-core processors in 2007. Project 4x4 represents system-level enthusiast enhancements and is designed for ultimate multi-tasking performance across gaming, digital video, processor-intensive and heavily threaded applications," the firm said.
While the software industry still has a lot of catching up to do to lets users completely harness multi-threaded programs for home use, it's still a very encouraging thing to see these steps being taken. Imagine having 8 Athlons or 8 Conroes sitting in one tiny box under your desk. Aside from the power bill, you'd be pretty happy.