RAM Modules

Rambus is a memory design standard developed by Rambus, Inc. Rambus modules are referred to as RDRAM (Rambus DRAM) because they use Fast Page Mode DRAM (Dynamic Random Access Memory) core memory and Rambus Signaling Level technology as the high-speed system interconnect. The RDRAM architecture arranges devices in a serial channel. Packetized commands and data are transferred along the channel on both edges of a 400 MHz clock. The data transfer rate is generally considered to be 1.6 GB per second because a two-byte-wide data path is generally used, multiplying the 800 MHz speed by two words. This data transfer rate is much faster than a conventional DRAM (or SDRAM) module. Rambus memory modules are called RIMM™s (Rambus In-line Memory Module). Because of the fast data transfer rate of these modules, a heat spreader (aluminum plate covering) is used for each module. The heat spreader wicks heat away to keep the module from overheating. Because the Rambus channel must be continuous, unused slots in a channel must be occupied by a CRIMM (Continuity Rambus In-line Memory Module), in order to complete the channel's connections. The nomenclature "ECC" stands for Error Correction Code. This is a feature that is used primarily in high-end units in today's computer industry. The ECC feature is only utilized if all memory slots are populated with ECC memory (or a continuity module). Some Compaq units were originally configured with 600 MHz or 700 MHz (712 MHz) RDRAM. The 800 MHz RDRAM listed above is downward compatible with these as shown under "Compatibility". In other words, if your unit was purchased with 600 MHz RDRAM, and you upgrade by adding a compatible Compaq 800 MHz RDRAM module, the unit will run all the memory at 600 MHz.