The Redwood parallel bus interface family addresses intra-board applications including processor, chipset and network chip connections. It is optimised for low latency and low power parallel bus applications, and enables the highest-pin bandwidth to reduce overall package, board, and system costs. Elements integrated into the Redwood technology include a 400MHz - 6.40GHz data rate range, low-voltage differential signaling, backwards compatibility with existing standards, such as HyperTransport, SPI-4 and RapidIO, allowing for easy integration into next-generation products. In order to achieve backwards compatibility, Redwood offers customers a range of frequency and voltage support.
Redwood parallel bus interface consists of the following blocks:
- FlexPhase circuit technology is a major departure from traditional circuit technologies. It enables precise, per bit, on-chip alignment of data and clock, eliminating the need for PCB trace length matching and PCB timing constraints. This results in logic systems that are simpler, more compact, lower in cost, and capable of multi-GHz data rates.
- DRSL (Differential Rambus Signaling Level) with LVDS (Low Voltage Differential Signaling) enables backward compatibility. DRSL is a differential signaling technology available in bi-directional and uni-directional versions that offers a high-performance, low-power, cost-effective solution for transmitting data on and off chip. DRSL uses a variable signal swing as low as 200 mV, enabling low-power operation, reduced electro-magnetic radiation (EMR) and scalability for lower process voltages in the future. LVDS support enables backward compatibility to industry standards such as HyperTransport, RapidIO, SPI-4, and other varieties of LVDS signaling.
- Variable Date Rate (VDR) delivers data rates of 1-to-10 times the speed of the clock, supporting a wide range of system clocks and data rates ranging from 400MHz - 6.40GHz.
After glancing through the information Rambus supplies about its new technology, it seems that the company simply invented another interface with the same concept as the HyperTransport or PCI-Express. The Redwood is compatible with HyperTransport and is not compatible with PCI-Express. As a result, we are going to have three different interfaces for personal computers and other similar devices. HyperTransport is already widely adopted, while Redwood is licensed by Sony and Toshiba for their consumer electronics products. PCI-Express is currently not compatible with conventional PCI (at least, there are some issues with compatibility) and this may delay its market introduction. Both HyperTransport and PCI-Express are free, while Rambus licenses its technology.
Currently it is really hard to tell who of the three interfaces will survive on the PC market as all of them have pros and cons, while there is hardly enough space for three different technologies in this industry.