Digital Semiconductor debuts latest PCI bridge

Electronic News, June 26, 1995

MAYNARD, MASS.--Digital Equipment Corp.'s Digital Semiconductor division launched its latest PCI-to-PCI bridge chip, a spin-off of its first bridge device unveiled last year which enables system designers to add PCI expansion slots to motherboards or multiple components to add-in cards.

The new 21052 was designed to use less power and yield better performance than the existing 21050--Digital's first PCI bridge device introduced last October--and with a cut in the price. "This should be especially attractive to the adapter card market," said Tracy Richardson, Digital Semiconductor's product marketing manager. "Getting the price down 40 to 50 percent from our current levels certainly is a big incentive."

In 5,000-unit volumes, the 21052 is priced at $16.90, a sharp reduction compared to the $28 for the company's first generation device. Most of the savings was realized by moving from a 208-pin design to a 160-pin PQFP, Mr. Richardson said.

Using a tighter clock skew than its earlier design, the 21052 lets motherboard OEMs build systems without having to purchase an external clock buffer or phase-lock loop, resulting in a $1 to $2 savings per system, according to Mr. Richardson.

Another primary objective was to reduce the power consumption. The 21052 operates from a 3.3-Volt power supply and tolerates 5V I/O connectors, allowing OEMs to build both single voltage and universal add-in cards, Mr. Richardson said. Typical power dissipation falls below 1 watt. The PCI bus standard, which allows 132MBytes per second data transfers at 33MHz, has gathered wide industry support for its well-defined specifications and interoperability, Mr. Richardson said. One limitation, however, is that it is limited by the number of "loads" it can accommodate. Today the architecture is defined to carry 10 loads--one load for each IC and two loads per PCI slot. The 21052 allows motherboard designers to add up to four additional PCI slots per device.

Industry acceptance of PCI has spawned a movement in the motherboard community to displace the ISA slots with PCI slots, Mr. Richardson said. Today's systems typically carry up to six ISA slots and no more than three PCI slots. "You run out of your 10-load limit pretty quickly. We've been approached by many vendors who want six to eight slots, and the PCI bridge does that."

Additionally, adapter card manufacturers can use the device to boost the functionality of add-in cards. Quad-Ethernet LAN cards carrying four Ethernet controllers or dual SCSI cards typify the kind of applications the device is geared toward, Mr. Richardson said.

Digital Semiconductor's list of systems OEMs for its PCI-to-PCI bridge device have included Hewlett-Packard and Digital Equipment Corp. itself as well as several add-in card manufacturers. Rival IBM has also been shipping its own PCI bridge product--the 2782351--which debuted at last year's Fall Comdex (EN, Nov. 7, 1994).

The 21052 will undergo final qualification and begin volume production in July. Samples are now available in limited quantities.