Formerly named Poseidon Technology, HotRail (San Jose, Calif.) had developed core logic for four- and eight-processor servers based on Advanced Micro Devices Inc.'s Athlon chip. But as AMD's attention shifted away from high-end servers, HotRail dropped that project and applied the technology to networking.

HotRail's new mission is to produce backplane transceiver chips and, later on, switch fabrics. The company also plans to license its technology to ASIC and FPGA vendors, among others.

The company this week unveiled plans for a transceiver operating with the TTL I/O standard. Future transceivers will work with other standards for I/O, said Elie Massabki, HotRail director of mixed-signal technology.

"It's a market that desperately needs more help," said Bob Merritt, communications analyst with Semico Research Corp.

The shift away from Athlon chip sets was painless, said HotRail executives. By the time the technology was ready, AMD had decided to concentrate on low-end PCs and asked HotRail to delay its introduction.

Hungry for immediate revenue, HotRail dropped the project altogether and began hunting for other areas to serve. "We realized most of our customers were communications companies," Massabki said.

Parallel I/O schemes can accommodate a faster data rate by adding more parallel lines. But that increases power consumption, and it consumes valuable pins in the case of ASICs. This means it gets more difficult to build a parallel-bus interface as the speed of data communications increases.

Startup Jazio is among the companies working to keep parallel buses workable at extremely high speeds. Another approach would be to reduce pins by eschewing the parallel interface entirely; along those lines, startup AANetcom Inc. has developed a serial interface for backplanes.

Clean signal

HotRail's method is to clean up the signal, thus allowing each channel in a parallel bus to run faster. The company has developed calibration circuitry that ensures data bits are aligned with clock pulses. The circuitry also performs byte alignment, keeping the incoming data paths synchronized and adjusting for any miscues.

The lack of timing precision is already becoming a problem with some high-speed interfaces, such as Rambus Inc.'s DRAM interface.

"If you look at most of the Intel-Rambus memory-system problems, a lot of them have to do with managing the data so it arrives at the same receiving site at the same time and in the cleanest possible form," Merritt said. "It's very difficult to arrange for all the signals to arrive at the same time because the Rambus interface is running so fast."

The same problem is hitting network processor vendors, as increased speeds mean the processor has less time to investigate each packet. "Every one of those guys has come to us and said they're out of pins [for parallel I/O]," said Richard Egan, HotRail vice president of marketing.

HotRail's first chip, the HRP2100, is a 200-MHz parallel transceiver for connecting line cards via a backplane. It accepts a TTL output through an 80-bit-wide interface, then serializes the data into 10 pairs of differential lines, for a total throughput of 16 Gbits/second in each direction. The signals must be received on the other end by another HRP2100 — or, in the future, by any device using the HotRail technology.

The chip is the first of several in the HotRail Channel family. Future transceivers will address other I/O options, Massabki said, with low-voltage differential signaling (LVDS) being a likely next candidate.

Transceiver plans

HotRail also will announce the SRP3100 serial transceiver for connecting line cards in separate chassis. The part, the first in the SkyRail Link chip family, transmits signals up to 30 meters across coax, twisted-pair or fiber-optic cable at speeds of up to 3.125 Gbits/s.

Both parts are made in 0.25-micron CMOS. The HRP2100 is due to begin production shipments this quarter at $129 in quantities of 1,000. The SRP3100 will follow with volume production in the third quarter, shipping at $37 in quantities of 1,000, or $34 for a 2.5-Gbit/s version.

To extend the technology into other areas, HotRail is licensing its technology as a core. An FPGA vendor is among the first licensees; another is a memory-chip vendor that plans to use HotRail's technology to develop an interface to replace Rambus in networks, where the PC-centric Direct Rambus technology comes up short. Both agreements are due to be disclosed later this quarter, Egan said.

Meanwhile, HotRail has one more product it hopes to develop: a switch fabric handling up to 256 ports. The company envisions 16 such chips being used together in a 2-Tbit/s switch, Egan said. HotRail plans to release its first switch fabric later this year.