Apr 04, 2002 Santa Clara, CA
A new class of communication chips for routers is pushing the limits for today's IC testers, thereby requiring the need for new advanced chip testing technologies, warned an official from networking-equipment giant Cisco Systems Inc.
Testing limits are a prime concern for Cisco since it develops and uses cutting-edge network processors, switch fabric chips, application-specific integrated circuits (ASICs) and other devices in its routers--most notably the company's top-of-the-line 12000 Series products. The 12000 is Cisco's high-end router for building Internet Protocol (IP) backbones that operate at speeds of 10 gigabits per second and beyond.
The 12000 reportedly uses a proprietary network processor--dubbed "Toaster," which is based on an ASIC design from IBM Corp.'s Microelectronics Division. The router also makes use of merchant switch-fabric devices from AMCC, IBM, and PMC-Sierra.
But the shift towards faster routers is creating some new and daunting challenges for Cisco and its semiconductor suppliers, especially for the development of next-generation devices and process technologies, said Matthias Kamm, a hardware engineer within the Internet Routing Group (IRG) at San Jose-based Cisco. IRG develops the company's high-end 12000 routers.
"Routers are pushing technology to the limits," Kamm said. "Routers are getting bigger and becoming more powerful, but power and heat are becoming real problems [in systems design]."
Cisco also faces other and often overlooked challenges in the arena, especially on the chip-testing front. "The test challenges for devices in routers have gone up dramatically," said Kamm, during a recent presentation at a conference sponsored by Agilent Technologies Inc. here. Palo Alto, Calif.-based Agilent is the test, measurement and chip spin-off of Hewlett-Packard Co.
New test arsenal
One of the major challenges is the ability to test next-generation chips, such as network processors and switch-fabric devices, he said. And lowering the cost of IC-test remains a major issue for the industry as a whole, prompting Cisco to embrace an assortment of technologies, such as built-in-self-test (BIST), boundry scan, and others, he added.
Others are also jumping on the low-cost, chip-testing bandwagon as well. For example, Intel Corp. has declared war on test costs by endorsing a chip-testing technology called "distributed test." Previously, Intel made use of a traditional but expensive chip-testing technology called "functional test" (see June 19 story).
Meanwhile, during the presentation, Kamm wasn't exactly endorsing Agilent's line of automatic test equipment (ATE). But the Cisco official did acknowledge that the networking-equipment giant has standardized its chip-testing requirements within IRG on one platform: Agilent's 93000 line of ATE.
And Cisco is currently and successfully testing high-speed parts on the 93000 platform, he added. Launched in 1999, Agilent's 93000 is a 1,024-pin system that supports data rates up to 1.25 gigabits per second. During a series of presentations here last week, Agilent gave a sneak preview of plans to upgrade its IC testers (see March 28 story).
Cisco also uses other testers within the company. For example, within its COT operations, Cisco has standardized on testers from Agilent, Credence and Teradyne, according to Kamm.
The networking-equipment giant doesn't directly test its chips in-house, but rather it uses a test subcontractor called Digital Testing Services (DTS). The Santa Clara, Calif.-based operation is a subsidiary of International Semiconductor Engineering Laboratories Inc., or ISE Labs. Fremont, Calif.-based ISE Labs is part of Taiwan test subcontracting giant ASE Test Ltd.
ISE makes use of ATE systems from Advantest, Agilent, Credence, Schlumberger and Teradyne. The test house specializes in testing high-speed, high-pin count devices for a slew a companies, including Cisco.
Testing 'Toaster'
DTS tests a range of devices for Cisco on Agilent's 93000 tester. Among the key chips for the 12000 router is Cisco's own "Toaster" network processor. "The network processor is one of the most challenging [devices] to test," Kamm said in an interview with SBN after the presentation.
Another key building block for a router is the switch-fabric device, which transports or sends high-speed packet data in a system. Cisco's 12000 router makes use of several switch-fabric chips, including one from IBM.
Today's switch-fabric IC from IBM is a 0.18-micron part with 800 or more pins. Geared for 1.25-Gbps applications, the 125-MHz chip has 64 internal links, but it also requires an external serial/deserializer (SerDes) device.
IBM's next-generation device is a 200-MHz part with more than 100 links-all based on 0.13-micron process technology and copper interconnects. The device's pin-count has been reduced to 512 I/Os but it now has an embedded SerDes device.
To test these devices in a cost-effective manner, Cisco embraces several chip-testing technologies, with the help of its semiconductor and ATE partners. "The first line of defense is DFT," he said. "You have to try to scan when possible."
The Cisco official was referring to a term called design-for-testability (DFT), which describes a methodology of lowering chip-testing costs. There are several emerging and competing DFT technologies that promise to lower chip-testing costs, such as BIST, boundry scan and others.
Cisco embraces both BIST and scan. For example, IBM incorporates DFT technologies like BIST and scan within its ASIC designs, which, in turn, are used by Cisco and most other router vendors, according to Kamm. "If you use ASICs, you tend to use scan and BIST," he said.
ASICs also require "structural test," he said, referring to another buzzword in the arcane ATE world that relates to DFT.
Palo Alto-based Agilent itself does not refer to its 93000 platform as a "structural" or "DFT" tester. The company's ATE system is a modular platform geared for DFT-like applications in system-on-a-chip (SoC) and other applications. "Agilent has done a good job in meeting our requirements," Kamm said.
Other ATE vendors have or are developing DFT-specific testers, including Advantest, Credence, and Teradyne.
