avoids the speed and capacity limits of the optical discs which most other gaming platforms rely on. Valve released the Steam platform for Windows computers in 2003 as a means to distribute Valve-developed video games such as Half-Life 2. It would later see release on the Mac OS X operating system in 2010 and was released on Linux in 2012 as well. By 2011, it controlled 70% of the market for downloadable PC games, with a userbase of about 40 million accounts. Origin, a new version of the Electronic Arts online store, was released in 2011 in order to compete with Steam and other digital distribution platforms on the PC. The period between 2004 and now saw the rise of many digital distribution services on PC, such as Amazon Digital Services, GameStop, GFWL, EA Store, Direct2Drive, GOG.com, and GamersGate. Digital distribution also slashes the cost of circulation, eliminates stock shortages, allows games to be released worldwide at no additional cost, and allows niche audiences to be reached with ease. However, most digital distribution systems create ownership and customer rights issues by storing access rights on distributor-owned computers. Games confer with these computers over the Internet before launching. This raises the prospect of purchases being lost if the distributor goes out of business or chooses to lock the buyer's account, and prevents resale (the ethics of which are a matter of debate). PC gaming technology Hardware Modern computer games place great demand on the computer's hardware, often requiring a fast central processing unit (CPU) to function properly. CPU manufacturers historically relied mainly on increasing clock rates to improve the performance of their processors, but had begun to move steadily towards multi-core CPUs by 2005. These processors allow the computer to simultaneously process multiple tasks, called threads, allowing the use of more complex graphics, artificial intelligence and in-game physics. Similarly, 3D games often rely on a powerful graphics processing unit (GPU), which accelerates the process of drawing complex scenes in realtime. GPUs may be an integrated part of the computer's motherboard, the most common solution in laptops, or come packaged with a discrete graphics card with a supply of dedicated Video RAM, connected to the motherboard through either an AGP or PCI-Express port. It is also possible to use multiple GPUs in a single computer, using technologies such as NVidia's Scalable Link Interface and ATI's CrossFire. Sound cards are also available to