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65nm “STB-on-a-chip” runs Linux

Sep 7, 2007 — by LinuxDevices Staff — from the LinuxDevices Archive — 302 views

Broadcom is sampling a highly integrated system-on-chip (SoC) for cable, satellite, and IP set-top boxes (STBs). Built on outsourced 65nm process technology, the BCM7405 “STB-on-a-chip” is based on a 400MHz MIPS32/16e processor core, runs Linux, and supports numerous video compression standards as well as networked personal video recorder (PVR) functionality.

Broadcom says its BCM7405 builds on several generations of BCM740x chips. However, it appears to be the first of Broadcom's STB chips based on 65nm process technology.

Broadcom outsources “leading-edge” chip fabrication to foundries TSMC and Chartered, according to semiconductor industry news source FabTech. The publication said that in recent corporate filings, Broadcom has reported experiencing “higher photomask and prototyping costs as well as design through verification costs” than were encountered in “previous node migrations.”

Broadcom describes the 65nm process used to build the BCM7405 as “the most advanced lithographic node for manufacturing semiconductors in large volumes today.” The technology's high transistor density is claimed to enable lower power consumption, smaller size, and higher levels of integration, for lower bill-of-materials costs and better performance.

Broadcom claims its new BMC7405 delivers “unprecedented levels of processor performance, memory bandwidth, graphics speed, system security, and peripheral integration.” Suggested applications include video recorders with whole-house content distribution over wired and wireless networks, and general video provider CPE (customer premises equipment).

Based on a 400MHz 32-bit MIPS processor core with MMU (memory management unit) and FPU (floating point unit) capabilities, the BCM7405 integrates a dedicated MIPS-based security co-processor, along with a 2D graphics controller with rich scaling and output interface capabilities. There's also a built-in audio co-processor, decoders for popular audio and video compression formats, and an ITU-R-656 decoder. Also present are a bevy of standard PC-style interfaces, including an analog modem, Ethernet, dual USB 2.0, dual SATA, infrared, and PCI expansion.

Broadcom BCM7405 function block diagram
(Click to enlarge)

Touted features and specifications include:

  • HD+SD simultaneous decode
  • Very high performance graphics scaling, blitting, and blending
  • An extensive set of 65nm analog cores including dual SATA-II ports, Fast Ethernet PHY, triple USB 2.0 ports, HDMI 1.3, integrated video and audio digital-to-analog converters, an RF modulator, and a UHF remote control receiver
  • PC client usage modes to support PC-oriented content viewing on televisions
  • A memory-to-memory DMA security module, programmable to support AES/1DES/3DES/CSS/CPRM/CPPM/DTCP copy protection algorithms/standards
  • Flexible standby modes
  • Security processor with “device personalization”
  • Up to 1 GB of low-cost DDR2 technology, at up to 800 MHz transfer rates
  • Double data rate Media Independent Interface (MII), for support of home networking chipsets

Broadcom also offers a BCM97405 reference design for the chip. It includes cable, satellite and terrestrial tuners, Smart Card, CableCARD, and DVB-CI interfaces, PCI and mini-PCI slots, and a number of test and debug interfaces, the vendor said.

Broadcom BCM97405 reference design architecture
(Click to enlarge)

In a statement, Dan Marotta, GM of Broadcom's broadband communications group, claimed that the BCM7405 represents “the industry's most advanced, highest performing, and most integrated solution for set-top boxes today.”

As quoted by Broadcom, Michelle Abraham, principal analyst at In-Stat, noted that, “With over 14 million PVR-enabled set-top boxes shipped in 2006, the market for PVRs in the IP, digital cable, and digital satellite markets is expected to grow by 63 percent by 2010.”


The BCM7405 is sampling to early access customers, along with the BCM97405 reference design. The design supports Linux and Windows CE, and comes with a “complete set of software drivers and APIs,” Broadcom said.

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