HP ProLiant SL170s Memory technology evolution: an overview of system memory t
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- HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 1
DRAM storage density and power consumption 4 Memory access time ...4 System bus timing...4 Memory bus speed ...5 Burst mode access ...5 technologies 12 Fully-buffered DIMMs ...15 Importance of using HP-certified memory modules in ProLiant servers 18 Conclusion ...18 For more information ...19 - HP ProLiant SL170s | 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 the different dynamic random access memory (DRAM) technologies. Processors use system memory to store the operating system, applications, and data - HP ProLiant SL170s | 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 SL170s | Memory technology evolution: an overview of system memory t - Page 4
time by the number of memory bus clocks. System bus timing A system bus clock controls all computer components that execute instructions or transfer data. The system chipset controls the speed, or frequency, of the system bus clock. The system chipset also regulates the traffic between the processor - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 5
Col Data Data Data Data 64b 64b 64b 64b NOTE: NOP = No Operation Instruction SDRAM technology DRAMs are asynchronous, that is, without a memory bus clock. the JEDEC developed the synchronous DRAM standard to reduce the number of system clock cycles required to read or write data. SDRAM uses a - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 6
a second clock signal that runs synchronously with the system bus clock. This means the system bus clock does not have to drive all the 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 4 - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 7
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 loading. If the - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 8
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 errors can cause applications and operating systems to crash, sometimes resulting in permanent - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 9
all HP ProLiant servers. ECC generating a Non-Maskable Interrupt (NMI) message that instructs the system to halt. ECC technology provided adequate protection for many more memory capacity in industry-standard servers: • Operating system support for increasing amounts of memory • Availability of low- - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 10
ECC does not provide failover 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 - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 11
to the server's user guide. In a system with three channels per system support or special software beyond the system BIOS. However, to support messaging and logging at the console along with messages in HP Systems Insight Manager, the operating system must have system management and agent support - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 12
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 - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 13
400 Mb/s, or 3.2 GB/s. Although the data bus is capable of running at these speeds, the command bus cannot. The use of strobes alleviated tight system timing requirements on the data bus. But the command bus does not use a strobe and must still meet setup times to a synchronous clock, so at - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 14
the commands, addresses, control 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 DDR3 DIMMs. • 1.5-V signaling reduces power consumption from the 1.8- V signaling for DDR2. DDR3 also - HP ProLiant SL170s | 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 SL170s | 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 the drop in capacity per channel was not a viable option. System designers had two choices: limit memory capacity so that fewer errors - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 17
of pins. In addition to communicating over the outbound lanes, the memory controller communicates configuration information with each AMB over the System Management bus or SMBus. The AMB is an intelligent chip that manages serial communication with the memory controller and parallel communication - HP ProLiant SL170s | Memory technology evolution: an overview of system memory t - Page 18
and requirements of the designated ProLiant server. To find the correct HP memory option kit, consult the server's user guide or the product QuickSpecs available at www.hp.com. Conclusion The constant need to boost memory performance for increasingly powerful system processors drives the development - HP ProLiant SL170s | 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
...................................................................................
4
Memory access time
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4
System bus timing
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4
Memory bus speed
...........................................................................................................................
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