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Posted: June 23rd, 2003
Written by: Adam Honek

New CSA bus for network traffic

It has been extensively known that the PCI bus can be a bottleneck should many devices housed on it all incline to interact collectively at any one time. The peak theoretical bandwidth of just 132MB/sec can quickly in such cases be prone to incur dismal efficiency. Streaming devices such as network adapters depend on bandwidth being available throughout their entire use, usually for as long as the machine is connected to a network infrastructure. With this mostly reflecting an “always on” scenario appears the need for a connection bus housing this ability. Gigabit (128MB/sec) and higher speed network adapters, switches, bridges and routers are all at the mercy of how fast the data can be passed on through them. A network is only as efficient as its weakest link and a good starting point for such analysis is the workstation connection itself. Gigabit via the PCI bus will at some point in its use (depending on other system component usage) hit a barrier determining its maximum throughout, usually much lower than its peak allowance. Sharing the PCI bus 132MB/sec throughput amongst competing PCI devices will ultimately reflect this trend be it less or more intrusive. Introducing a separate network only orientated bus with 266MB/sec dedicated to networking I/O lifts this blockage freeing the PCI bus entirely from this role, and in exchange allowing it to give back more bandwidth to other devices that call for it, such as sound cards, firewire/USB2 cards, or TV/Multimedia cards. Lifting the performance burden from high end consumer PC’s/entry level workstations paves the way for much more proficient networking; a good demonstration of Intel’s forward planning adapting technology to areas where the industry is steadily expanding. We must emphasize that CSA is only a bus or data highway as one might think of it, for gigabit network chipsets to harness the ample bandwidth they must also support CSA, currently only Intel itself has such offerings but the good news is that many others should follow within the near future. While the outlook seems to echo a growing trend most offices today still mainly use 100Mbit connections thus CSA although very much a positive feature to have currently might reside unused on motherboards sold today. Enterprise solutions benefiting from PCI-X remain unaffected but these are mostly server orientated. The question most people will surely ask themselves is how useful CSA presently is given its extra cost outlay for a technology that is yet to penetrate the market by storm.


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