Technologies for the ProLiant ML570 G3 and ProLiant DL580 G3 Servers Technology Brief

and the ProLiant DL580 G3 use DDR2-400 memory and interleaving to improve memory performance
and decrease this performance gap.
DDR-2 memory
DDR-2 SDRAM is the second generation of DDR SDRAM. In contrast to the first generation, DDR-2
memory operates at an even lower voltage (1.8V) to further reduce power consumption; uses higher
clock frequencies to increase data transfer rates, and uses on-die termination control to improve signal
quality. At 200 MHz (double-clocked to an effective 400 MHz), DDR-2 increases memory bandwidth
to 3.2 GB/s.
In DDR memory, an external termination resistor is added to the system board to improve signal
quality and reduce noise for the memory signals. This reduces the likelihood of a signal reflecting, or
bouncing back, toward the driving source. DDR-2 memory, on the other hand, moves this resistor into
the silicon of the memory itself. This reduces signal reflection and therefore improves signal quality
(Figure 4).
Refer to the technology brief titled “
Memory technology evolution: an overview of system memory
technologies” for additional information about DDR-2 memory technology.
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Figure 4. On-die termination reduces the amount of signal reflection to improve signal quality.
Memory interleaving
To reduce latencies and improve performance, there are three different types of memory interleaving
within the ProLiant ML570 G3 and DL580 G3 servers: two-way (dual channel) interleaving,
interleaving within the XMB memory controller, and interleaving across multiple XMB memory
controllers. To simplify the descriptions, the following sections describe how interleaving works when
using single-rank DIMMs. The same concepts apply for dual-rank DIMMs.
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Available on the ISS Technology papers website at http://h18004.www1.hp.com/products/servers/technology/whitepapers/adv-
technology.html.
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