HP ProLiant DL280 Memory technology evolution: an overview of system memory te - Page 12

Advanced memory technologies, Rambus DRAM, Double Data Rate SDRAM technologies, DDR1

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Advanced memory technologies Advanced memory technologies fill the growing performance gap between memory and processor despite the gains made possible by SDRAM. The industry has developed several technologies to boost system performance using the latest high-speed processors (Figure 8). Figure 8. Peak bandwidth comparison of SDRAM and advanced SDRAM technologies Rambus DRAM Rambus DRAM (RDRAM) is a memory technology introduced in the late 1990s to achieve faster memory throughput than SDRAM. Unlike SDRAM, Rambus used a high-speed serial connection to move data from memory modules to the system. The Rambus design consisted of three key elements: RDRAMs, Rambus ASICs, and a Rambus Channel interconnect. Unlike the later FB-DIMM standard, the Rambus system used a multi-drop serial bus to communicate with each RDRAM chip rather than using an advanced memory buffer (AMB). RDRAM delivered better memory bandwidth than SDRAM, but it required a different memory bus design and significantly more expensive RDRAM chips. Double Data Rate (DDR) SDRAM, with a design similar to SDRAM but having higher bandwidth and lower costs, replaced RDRAM in server designs. Double Data Rate SDRAM technologies Double Data Rate (DDR) SDRAM technology doubles the SDRAM data transfer rate without increasing the frequency, or speed, of the memory clock. This section describes three generations of DDR SDRAM technology. DDR1 To develop the first generation of DDR SDRAM (DDR1), designers made enhancements to the SDRAM core to increase the data rate. These enhancements include prefetching, double transition clocking, strobe-based 12

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Advanced memory technologies
Advanced memory technologies fill the growing performance gap between memory and processor despite
the gains made possible by SDRAM. The industry has developed several technologies to boost system
performance using the latest high-speed processors (Figure 8).
Figure 8
. Peak bandwidth comparison of SDRAM and advanced SDRAM technologies
Rambus DRAM
Rambus DRAM (RDRAM) is a memory technology introduced in the late 1990s to achieve faster memory
throughput than SDRAM. Unlike SDRAM, Rambus used a high-speed serial connection to move data from
memory modules to the system. The Rambus design consisted of three key elements: RDRAMs, Rambus
ASICs, and a Rambus Channel interconnect. Unlike the later FB-DIMM standard, the Rambus system used a
multi-drop serial bus to communicate with each RDRAM chip rather than using an advanced memory buffer
(AMB).
RDRAM delivered better memory bandwidth than SDRAM, but it required a different memory bus design
and significantly more expensive RDRAM chips. Double Data Rate (DDR) SDRAM, with a design similar to
SDRAM but having higher bandwidth and lower costs, replaced RDRAM in server designs.
Double Data Rate SDRAM technologies
Double Data Rate (DDR) SDRAM technology doubles the SDRAM data transfer rate
without increasing the
frequency, or speed, of the memory clock. This section describes three generations of DDR SDRAM
technology.
DDR1
To develop the first generation of DDR SDRAM (DDR1), designers made enhancements to the SDRAM core
to increase the data rate. These enhancements include prefetching, double transition clocking, strobe-based
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