Chapter 2. Architecture and technical overview 432.2.4 Memory accessEach POWER7 processor chip has two DDR3 memory controllers, each with four memorychannels (enabling eight memory channels per POWER7 processor). Each channel operatesat 6.4 Gbps and can address up to 32 GB of memory. Thus, each POWER7 processor chip iscapable of addressing up to 256 GB of memory.Figure 2-5 gives a simple overview of the POWER7 processor memory access structure.Figure 2-5 Overview of POWER7 memory access structure2.2.5 Flexible POWER7 processor packaging and offeringsPOWER7 processors have the unique ability to optimize to various workload types. Forexample, database workloads typically benefit from fast processors that handle hightransaction rates at high speeds. Web workloads typically benefit more from processors withmany threads that allow the breakdown of Web requests into many parts and handle them inparallel. POWER7 processors have the unique ability to provide leadership performance ineither case.POWER7 processor coresThe base design for the POWER7 processor is an 8-core processor with 32 MB of on-chip L3cache (4 MB per core). However, the architecture allows for differing numbers of processorcores to be active: 4-cores or 6-cores, as well as the full 8-core version. For the PS703 andPS704 blades, only the full 8-core version is used.The L3 cache associated with the implementation is dependant on the number of activecores. For the 8-core version, this means that 8 x 4 = 32 MB of L3 cache is available.Note: In certain POWER7 processor-based systems (including the PS700, PS701, PS702,PS703 and PS704) only one memory controller is active.AdvancedBuffer ASICChipMemoryControllerMemoryControllerPOWER7 processor chipDual integrated DDR3 memory controllers High channel and DIMM utilization Advanced energy management RAS advancesEight high-speed 6.4 GHz channels New low-power differential signallingNew DDR3 buffer chip architecture Larger capacity support (32 GB/core) Energy management support RAS enablementDDR3 DRAMsP7 Core P7 Core P7 Core P7 CoreP7 Core P7 Core P7 Core P7 Core
