HP ProLiant SL390s Memory technology evolution: an overview of system memory t
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- HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 1
8 Memory protection technologies ...10 Advanced memory technologies ...12 Rambus DRAM...12 Double Data Rate SDRAM technologies 12 Fully-buffered DIMMs ...15 Importance of using HP-certified memory modules in ProLiant servers 18 Conclusion ...18 For more information ...19 Call to action ...19 - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 2
we use in HP ProLiant servers, and describes how we evaluate these technologies. It also briefly summarizes the evolution of server memory and explores terms of price, performance, reliability, and backward compatibility, and then implement the most promising technologies in ProLiant servers. Basic - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 3
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 DRAM memory writes data to a cell, the memory controller selects the data's location. The memory controller - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 4
bus timing A system bus clock controls all computer components that execute instructions or transfer data. The system chipset controls the speed, or . These clocks use various clock multiplier and divider circuits to generate multiple signals. All these signals derive from the main system bus - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 5
Memory timing and maximum DRAM speed control memory subsystem speed. The server BIOS sets the memory system speed based on the fastest common frequency of Data Data Data 64b 64b 64b 64b NOTE: NOP = No Operation Instruction SDRAM technology DRAMs are asynchronous, that is, without a memory bus - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 6
. Simultaneously, a phase-locked loop chip on a registered DIMM generates a second clock signal that runs synchronously with the system bus DRAMs used as well as the number of memory blocks, called ranks, the DIMM supports. Single-sided and double-sided DIMMs Each DRAM chip on a DIMM provides either - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 7
use multiple memory buses. If the total number of ranks in the populated DIMM slots exceeds the maximum number of loads, the chipset can support, the server may not boot properly or it may not operate reliably. Some systems check the memory configuration while booting to detect invalid memory bus - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 8
To prevent such memory-related problems, we advise our customers to use only HP-certified DIMMs, which are available in the memory option kits for each ProLiant server (see the "Importance of using HP-certified memory modules in ProLiant servers" section). Another important difference between single - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 9
all HP ProLiant servers. ECC detects both single-bit and multi-bit errors in a 64-bit data word; it corrects single-bit errors. ECC encodes information in a block of 8 bits to recover a single-bit error. When the DIMM writes data to memory, ECC uses a special algorithm to generate values called - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 10
capability. If there is a memory failure, you must shut down the system before replacing the memory. The latest generation of HP ProLiant servers offers several forms of Advanced Memory Protection that provide increased fault tolerance for applications requiring higher levels of availability. Memory - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 11
server availability and memory reliability without service intervention or server For more information, refer to the server's user guide. In a system with three support or special software beyond the system BIOS. However, to support messaging and logging at the console along with messages in HP - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 12
to SDRAM but having higher bandwidth and lower costs, replaced RDRAM in server designs. Double Data Rate SDRAM technologies Double Data Rate (DDR) memory clock. This section describes three generations of DDR SDRAM technology. DDR1 To develop the first generation of DDR SDRAM (DDR1), designers made - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 13
clock frequencies of 100 MHz and 133 MHz, respectively. Stub-Series Terminated Logic_2 (SSTL_2) low-voltage signaling technology The signaling the module. They are best suited for servers with high memory capacities. DDR2 DDR2 is the second generation of DDR SDRAM technology. It provides data rates - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 14
DIMM with 240-pin interface DDR3 DDR3, the third-generation of DDR SDRAM technology, makes further improvements in bandwidth reducing the number of stubs and their length. This feature requires the controller to support "write leveling" on DDR3 DIMMs. • 1.5-V signaling reduces power consumption from - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 15
industry based the DDR-SDRAM naming convention on the actual peak data transfer rate in MB/s. For example, PC266 is equivalent to PC2100 (64 bit * 2 * 133 MHz = 2.1 GB/s or 2100 MB/s). DDR3 SDRAM DIMM manufacturers produce two types of DIMMs: Unbuffered DIMMs (UDIMM) and Registered DIMMs (RDIMM). - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 16
these factors decrease the number of supportable DIMMs per channel. For example, Figure 12 shows the number of loads supported per channel at data rates ranging density. For future generations of high-performance servers, neither option was acceptable. New server designs require improved memory - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 17
uses more power, and has increased latency. As a result, the industry has not implemented FB-DIMMs for DDR3. Instead, engineers have increased server memory capacities by designing systems with Non-Uniform Memory Access (NUMA) architectures, which feature up to four memory channels for each CPU. 17 - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 18
and testing needed for servers because it adds to the price of DIMMs. We use proprietary diagnostic tools and specialized server memory diagnostic tests that exceed industry standards to ensure the highest level of performance and availability for HP ProLiant servers. The cost related to - HP ProLiant SL390s | Memory technology evolution: an overview of system memory t - Page 19
Resource description JEDEC Web site HP ProLiant Server Memory web page DDR3 memory technology, technology brief Web address http://www.jedec.org http://h18004.www1.hp.com/products/servers/options/memorydescription.html http://h20000.www2.hp.com/bc/docs/support/SupportManual /c02126499/c02126499.pdf
Memory technology evolution: an overview
of system memory technologies
Technology brief, 9
th
edition
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
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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5
Bank interleaving
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6
Increased bandwidth
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6
Registered SDRAM modules
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6
DIMM configurations
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6
DIMM error detection/correction technologies
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8
Memory protection technologies
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10
Advanced memory technologies
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12
Rambus DRAM
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12
Double Data Rate SDRAM technologies
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12
Fully-buffered DIMMs
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15
Importance of using HP-certified memory modules in ProLiant servers
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18
Conclusion
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18
For more information
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19
Call to action
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19