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General Information -

Rambus Dynamic Random Access Memory (RDRAM) -

RDRAM is a computer memory architecture.  A single RDRAM can deliver up to 1.6 gigabytes of data per second over the Rambus Channel – a narrow, high-speed bus. 

RDRAM can be implemented using with RIMM modules as RDRAM for desktop computers and SO-RIMM modules for portables. Motherboard manufacturers started using the PC 800 RDRAM design in early 2000. 

RDRAM uses the RIMM ( Rambus Inline Memory Modules ) connector ( shown below ).

RDRAM

According to Rambus, "the RIMM module conforms to the standard DIMM form factor, but it is not pin-compatible. Its architecture is based on the electrical requirements of the Direct Rambus Channel, a high-speed bus operating at a clock rate of 400MHz which enables a data rate of 800MHz (data is clocked on both clock edges). A two byte-wide data channel is used resulting in a peak data transfer rate of 1.6 Gbytes per second. The bus uses transmission line characteristics to maintain high signal integrity."

"Up to three RIMM modules may be used on a PC desktop motherboard. The Rambus Channel extends from the controller through each RIMM module in a continuous flow until the Channel termination is reached. Low-cost continuity modules are used to maintain Channel integrity in systems having less than three RIMM modules."

"An on-board SPD (Serial Presence Detect) PROM chip is used to provide initialization information to the system processor on power-up. This technique assures compatibility across all Direct Rambus RDRAM manufacturing partners producing various density DRAM devices."

SO-RIMM -

These modules should be able to deliver up to two times the memory bandwidth of comparable SDRAM memory systems and are suited for low power applications such as portable computers.

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