HP ProLiant XL730f Memory technology evolution: an overview of system memory t
HP ProLiant XL730f Manual
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- HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 1
DDR-3 ...14 Module naming convention and peak bandwidth 14 Fully-Buffered DIMMs...15 FB-DIMM architecture...16 Challenges ...17 Rambus DRAM ...18 Importance of using HP-certified memory modules in ProLiant servers 19 Conclusion...19 For more information...20 Call to action ...20 - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 2
backward compatibility and implements the most promising technologies in ProLiant servers. HP is committed to providing customers with the most reliable processor. Main memory consists of DRAM chips that can be packaged in a variety of ways on dual inline memory modules (DIMMs) for the notebook, desktop - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 3
/command bus is a set of traces that carry signals identifying the location of data in memory. The command portion of the address/command bus conveys instructions such as read, write, or refresh. When FPM or EDO memory writes data to a particular cell, the location where the data will be written is - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 4
DRAM. For synchronous DRAM, the time is converted to number of memory bus clocks. Chipsets and system bus timing All computer components that execute instructions or transfer data are controlled by a system bus clock. The system chipset controls the speed, or frequency, of the system bus clock and - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 5
components, either the rest of the system or the component itself must wait one or more additional clock cycles for data or instructions due to clock resynchronization. In contrast, synchronized components know on which clock cycle data will be available, thus eliminating these timing delays - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 6
with every clock cycle after the first access (6-1-1-1) before the memory controller has to send another CAS. Figure 4. Burst mode access. NOP is a "No Operation" instruction. Clock Command Address Data Active NOP NOP Read NOP NOP NOP NOP NOP NOP Row Col Data Data Data Data 64b 64b 64b 64b - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 7
Bank interleaving SDRAM divides memory into two to four banks for simultaneous access to more data. This division and simultaneous access is known as interleaving. Using a notebook analogy, two-way interleaving is like dividing each page in a notebook into two parts and having two assistants to each - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 8
DIMM Configurations Single-sided and double-sided DIMMs Each DRAM chip on a DIMM provides either 4 bits or 8 bits of a 64-bit data word. Chips that provide 4 bits are called x4 (by 4), and chips that provide 8 bits are called x8 (by 8). It takes eight x8 chips or sixteen x4 chips to make a 64-bit - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 9
four DIMM slots, the chipset may only be capable of supporting two dual-rank DIMMs or four single rank DIMMs. If problems, customers should only use HP-certified DIMMs available in the memory option kits for each ProLiant server (see the "Importance of using HP-certified memory modules in ProLiant - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 10
Memory channel interleaving Multi-core processors running multi-threaded applications pose a significant challenge to the memory subsystem. The processor cores share the bandwidth of the memory bus; therefore, the multi-core processor's performance is limited by the memory bus bandwidth. Even with - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 11
Advanced memory technologies Despite the performance improvement in the overall system due to use of SDRAM, the growing performance gap between the memory and processor must be filled by more advanced memory technologies. These technologies, which are described on the following pages, boost the - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 12
Double transition clocking Standard DRAM transfers one data bit to the bus on the rising edge of the bus clock signal, while DDR-1 uses both the rising and falling edges of the clock to trigger the data transfer to the bus (Figure 10). This technique, known as double transition clocking, delivers - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 13
. DDR-2 DDR-2 SDRAM is the second generation of DDR SDRAM. It offers data rates of up to 6.4 GB/s, lower power consumption, and improvements in packaging. At 400 MHz and 800 Mb/s, DDR-2 increases memory bandwidth to 6.4 GB/s, which is 800 percent more than original SDRAM. DDR-2 SDRAM achieves this - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 14
signals, and clocks) improves signal integrity by reducing the number of stubs and their length. This feature requires the controller to support "write leveling" on DDR-3 DIMMs. • 1.5-V signaling (compared to 1.8 V for DDR-2) for lower power consumption • A thermal sensor integrated on the DIMM - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 15
. The electrical load accumulates as DIMMs are added. These factors decrease the number DIMMs per channel that can be supported as the bus speed increases. For example, Figure 14 shows the number of loads supported per channel at data rates ranging from PC 100 to DDR-3 1600. Note that the number of - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 16
Consequently, JEDEC developed the Fully-Buffered DIMM (FB-DIMM) specification, a serial interface that eliminates the parallel stub-bus topology and allows higher memory bandwidth while maintaining or increasing memory capacity. FB-DIMM architecture The FB-DIMM architecture has serial links between - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 17
Challenges The challenges for the FB-DIMM architecture include latency and power use (thermal load). Memory latency is the delay from the time the data is requested to the time when the data is available from the memory controller. The FB-DIMM architecture increases this latency in two ways: - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 18
rate at 1.2 GHz. This allows for plenty of timing margin in the design of the memory controller. Figure 17. Rambus DRAM RDRAM is capable of supporting up to 32 RDRAM devices on one memory channel while maintaining a 1.2-GHz data rate. Through the use of a repeater chip, even more devices can be - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 19
to 32 devices, imposing an upper limit on memory capacity supported by a single bus. Use of repeater chips enables ProLiant server for which they are designated. Therefore, they prevent improper mixing of single-rank and dual-rank DIMMs. HP memory option kits are listed in each server's user guide - HP ProLiant XL730f | Memory technology evolution: an overview of system memory t - Page 20
refer to the resources listed below. Resource description JEDEC Web site HP Advanced Memory Protection Fully-Buffered DIMM technology in HP ProLiant servers Web address http://www.jedec.org http://h18004.www1.hp.com/products/servers/technology/whitepapers/advtechnology.html#mem http://h18004.www1
Memory technology evolution: an overview
of system memory technologies
technology brief, 8
th
edition
Abstract
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2
Introduction
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2
Basic DRAM operation
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2
DRAM storage density and power consumption
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4
Memory access time
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4
Chipsets and system bus timing
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4
Memory bus speed
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5
Burst mode access
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5
SDRAM technology
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6
Bank interleaving
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7
Increased bandwidth
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7
Registered SDRAM modules
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7
DIMM Configurations
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8
Single-sided and double-sided DIMMs
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8
Single-rank, dual-rank, and quad-rank DIMMs
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8
Rank interleaving
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9
Memory channel interleaving
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10
Advanced memory technologies
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11
Double Data Rate SDRAM technologies
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11
DDR-1
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11
DDR-2
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13
DDR-3
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14
Module naming convention and peak bandwidth
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14
Fully-Buffered DIMMs
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15
FB-DIMM architecture
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16
Challenges
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17
Rambus DRAM
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18
Importance of using HP-certified memory modules in ProLiant servers
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19
Conclusion
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19
For more information
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20
Call to action
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20