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Silicon Interconnect Technologies
One of the biggest points of confusion surrounding these standards is the emerging role of HyperTransport. This technology, developed by Advanced Micro Devices (AMD), was initially seen as a competitor to 3GIO. This perception had many people feeling a "bus war" between Intel and AMD was imminent, with separate cards, separate standards. No one, not AMD, Intel or anyone else, wanted that.
The HyperTransport Technology Consortium is instead pushing this packetized standard for interconnecting silicon devices, as opposed to replacing PCI-X and conventional PCI. This is a crucial difference. HyperTransport will be competing with 3GIO for communication between silicon devices on system boards.
This extends far beyond PC and server architecture. There won't be a bus war, at least on the expansion-card level. At the silicon-device interconnect level, may the best technology win.
HyperTransport can reach peak aggregate bandwidth of 12.8 Gbps. IT departments and consumers will not have to worry about it, and the competition can only be good for the market.
Indeed, many of the companies that support HyperTransport are backing it mostly because it's not an Intel standard. Intel has a huge influence on the silicon and PC markets, and despite its everything-is-rosy outlook, many companies want to see AMD flourish just so there's a viable alternative to Intel. Cisco Systems backs HyperTransport. Cisco envisions using HyperTransport on its switch and router platforms to improve reliability and connection speeds between discrete silicon.
Charter members of the HyperTransport Technology Consortium are AMD, API Networks, Apple Computer, Cisco, NVidia Corp., PMC-Sierra, Sun Microsystems and Transmeta Corp. In late 2000 the HyperTransport Technology Consortium brought in new members, including Acer Laboratories, Altera Corp., Broadcom Corp., Marvell Technology Group, Nokia and Xilinx. These new members, particularly Nokia, lend some real weight to HyperTransport's bid to become a leading chip interconnect technology.
If all goes well, HyperTransport will nicely complement PCI, PCI-X, 3GIO and InfiniBand. With all the support behind 3GIO, the HyperTransport Technology Consortium has wisely decided that HyperTransport should be positioned as a silicon-device interlink, as opposed to a separate card I/O standard. AMD will also implement this technology into its Hammer line of processors, due out at the end of the year. Hammer is AMD's answer to Intel's Itanium 64-bit processor. Video powerhouse NVidia has incorporated HyperTransport into its line of system main-board chips, called Nforce.
RapidIO, however, will give HyperTransport competition in the chip interconnect arena. RapidIO is another specification for silicon-device interconnects. Its main focus is embedded applications, particularly in the telecommunications industry and parts of the networking industry. The current specification is purely parallel; approval for the finished serial version of the specification is expected later this month.
RapidIO is a 3.3-volt specification, as opposed to HyperTransport, which is 1.2 volt. The advantage of RapidIO is that many existing silicon devices use 3.3 volt, whereas devices using 1.2 volts are hard to find. RapidIO also enjoys support from Motorola and IBM, which will be using the standard for the front-side bus of the PowerPC processors in its RS/6000 line and Apple Macintosh. Even with this kind of support, we expect RapidIO to find its greatest successes in the embedded market, as opposed to the PC market.
Also interesting is that RapidIO is layered, meaning there are separate protocol and physical layers. This feature makes using current physical designs easy with the RapidIO protocol. This is particularly true of RapidIO's upcoming serial specification, which will use a lot of the same physical level components as InfiniBand, reducing costs and development time for silicon manufacturers.
So what does all of this mean for network managers faced with buying decisions this year? That depends. In 2004, 3GIO will start being implemented for PC expansion and interconnects for home, corporate desktop, workstation and server-class machines. Between now and then, the standard PCI specification will remain in use for home and corporate desktop machines. On the workstation and server fronts, you will see PCI-X, DDR PCI-X and QDR PCI-X until the release of 3GIO.
When it comes to PC slot architectures, pay attention to PCI-X and 3GIO evolution, which should be refreshingly simple. The backers of both standards are paying careful attention to both software compatibility issues and IT technology investment issues. You can now buy PCI-X cards and expect to get a long healthy life out of them. But keep your eye out for 3GIO developments.
InfiniBand will continue to play a role mostly as a storage and cluster server interconnect for data centers for very large clusters. In the silicon-device interconnect area, HyperTransport and RapidIO will duke it out. But unless you're an electrical engineer or have a manufacturing concern, these technologies are interesting, but they won't affect buying decisions.
Steven J. Schuchart Jr. covers storage and servers for Network Computing. Previously he worked as a network architect for a general retail firm, a PC and electronics technician, a computer retail store manager, and a freelance disc jockey. Send your comments on this article to him at sschuchart@nwc.com.
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