Client server converges PC/appliance architectures

Client server converges PC/appliance architectures
The low-cost appliance industry is being driven by the high-performance PC industry. That's because the appliances are designed as clients that rely on the resources of a central home server or gateway. In fact, the proliferation of clients will drive the consumption of very high-performance PC-style CPUs into the future.

Architecturally, the PC — while it will still have some of the same functionality and features — will evolve into the "home media server," focused on managing the distributed computing environment that is taking form in the home. Such a new server will be the central resource controller of what might be called the digitally connected home. It will depend on a fat server sharing resources among thin — low-cost — clients.

Most customers are very sensitive to cost, so a visit to the computer store typically results in purchase of a PC in the $600 range — monitor excluded. These machines might have a hardware bill of materials of a little over $400, and it is possible today to equip a PC in this price range with a 2-GHz AMD Athlon processor. Fortunately, if the PC is not used for advanced games but for word processing or Web browsing, the 1-GHz processor now provided is quite adequate. Customers would like to have, say, 2-GHz performance, but they would also like to pay less than even $600. There is a way that this can be achieved.

If homes were equipped with a central media server box, a low-cost PC-client could access the resources of the server. The server, equipped with a high-frequency AMD Athlon processor, would perform all the workload required by the connected PC-clients. Application software, such as word processors or Web browsers, would run on the server. Clients would be reduced to rendering the screen image produced by the server on behalf of the PC-client and handling physical input/output. To the user, the experience would not be discernibly different from using a conventional PC. However, a PC-client can be constructed from RISC-based (low-cost) system-on-a-chip devices with a bill of materials of $120.

There is no need for a PC-client to be equipped with: its own hard drive, extensive amounts of RAM and flash memory or any of the other devices that are provided by the central media server. It is relatively easy to build a low-power portable PC-client at acceptable cost. Although a client is based on a low-end RISC CPU, the server still supports use of an X86 browser. PC users have become accustomed to the standard of Web access established by the PC industry and they are unwilling to accept the universally inferior experience offered by RISC-based browser products. It is technically possible to resolve the relevant RISC software development hurdles; it is just much simpler and less expensive to pursue the X86-based server path.

For example, Microsoft's Windows XP operating system supports this client-server architecture. Via Remote Services, a user can access his or her work desktop and file shares from any enabled PC-client or remote PC. It is also possible to use Unix-derived operating systems with the same hardware architecture — Linux and QNX have the necessary support. In particular, QNX has Qnet technology, which is especially efficient and versatile at supporting networked compute and I/O resources.

Client-server architectures are not new. Several technology and marketing developments now make them the most appropriate methodology:

• AMD Athlon CPU frequencies are going so high that most software applications don't need all the performance.
  
• Customers are demanding lower cost and better value.
  
• Major software providers have evolved architectures to support the client-server approach.
  
• There is demand and "vision" for a range of specialized peripheral appliances, which can only be built at low-cost if they rely on the resources of a central server.
  
• Some of these devices support information access, others support entertainment, such as MP3 music players.
  
• There is a large demand for the distribution of digital video around the home; this distribution must support Personal Video Recording (PVR) from any display location.

Each home appliance requires coordination of information and resources, and users will insist that there is little or no software administration required. Additionally, there is a need for a whole-house information gateway and data resource. A central resource simplifies such tasks as Internet policing (parental control), and sharing access to printers, DVD player, file systems, digital TV tuners and other peripherals.

The development of PC-clients is significant to the development and evolution of this new home media server architecture. The introduction of STB clients is equally significant to the video entertainment industry and requires special attention. STB developers have been struggling to develop low-cost hardware platforms capable of supporting both PVR and execution of the advanced user interfaces and applications required by the next-generation boxes. Technically ideal would be a box with the performance and resources of a PC, but the cost would be prohibitive.

The solution is to continue building the low-cost boxes the industry is familiar with. These are generally based on integrated single-chip devices, which already incorporate an MPEG-2 video decoder. An STB client does not require a tuner to receive a TV signal; now, the signal is sent over a network from the media server and the digital video signal is captured by the media server's own tuners or played back from the hard disk used by the server. The STB client relies on the Athlon CPU in the server to do all the heavy software work.

The media server is the most expensive component of the home system, but it does offer support for multiple low-cost clients around the home. The same media server used for video distribution supports PVR and PC-clients as well as information appliances and MP3 players. The utility and value to the home user is unsurpassed by any other architecture. Traditionally, purchase of an STB has been subsidized by video entertainment broadcasters via regular subscription to movie channels and the like. There is no reason these subsidies could not also apply to the media server purchases.

AMD not only has been investigating the potential of this new server but has developed a reference design. Other codevelopers have reference designs for the various subsystems that are linked in the home network: the personal server, the PC-client and the set-top box. In fact, a common hardware design can be used for both client types — the difference is mainly in the video output method. PC monitors (and HDTV) use progressive image scanning; conventional TVs use interlaced scanning. Other companies are working on clients to support information access, MP3 music and more. These appliances will be particularly attractive to the value-oriented customer.

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