Meet the Power 795—the RISC Mainframe

The IBM POWER 795 could be considered a RISC mainframe. A deep dive session on the Power 795 at Enterprise 2013 in early October presented by Patrick O’Rourke didn’t call the machine a mainframe. But when he walked attendees through the specifications, features, capabilities, architecture, and design of the machine it certainly looked like what amounted to a RISC mainframe.

Start with the latest enhancements to the POWER7 chip:

  • Eight processor cores with:

12 execution units per core

4 Way SMT per core – up to 4 threads per core

32 Threads per chip

L1: 32 KB I Cache / 32 KB D Cache

 L2: 256 KB per core

 L3: Shared 32MB on chip eDRAM

  • Dual DDR3 Memory Controllers

100 GB/s Memory bandwidth per chip

  • Scalability up to 32 Sockets

360 GB/s SMP bandwidth/chip

20,000 coherent operations in flight

Built on POWER7 and slated to be upgraded to POWER8 by the end of 2014 the Power 795 boasts a number of new features:

  • New Memory Options
  • New 64GB DIMM enable up to 16TB of memory
  • New hybrid I/O adapters will deliver Gen2 I/O connections
  • No-charge Elastic processor and memory days
  • PowerVM will enable up an 20 LPARs per core

And running at 4.2 GHz, the Power 795 clock speed starts to approach the zEC12 at 5.5 GHz while matching the clock speed of the zBC12.

IBM has also built increased flexibility into the Power 795, starting with turbo mode which allows users to turn on and off cores as they manage power consumption and performance. IBM also has enhanced the concept of Power pools, which allows users to group systems into compute clusters by setting up and moving processor and memory activations within a defined pool of systems, at the user’s convenience. With the Power 795 pool activations can be moved at any time by the user without contacting IBM, and the movement of the activations is instant, dynamic, and non-disruptive. Finally, there is no limit to the number of times activations can be moved. Enterprise pools can include the Power 795, 780, and 770 and systems with different clock speeds can coexist in the same pool. The activation assignment and movement is controlled by the HMC, which also determines the maximum number of system in any given pool.

The Power 795 provides three flavors of capacity of demand (CoD). One flavor for organizations that know they will need the extra capacity that can be turned on through easy activation over time. Another is intended for organizations that know they will need extra capacity at predictable times, such as the end of the quarter, and want to pay for the added capacity on a daily basis. Finally, there is a flavor for organizations that experience unpredictable short bursts of activity and prefer to pay for the additional capacity by the minute. Actually, there are more than the three basic flavors of CoD above but these three will cover the needs of most organizations.

And like a mainframe, the Power 795 comes with extensive hardware redundancy.  OK, the Power 795 isn’t a mainframe. It doesn’t run z/OS and it doesn’t do hybrid computing. But if you don’t run z/OS workloads and you’re not planning on running hybrid workloads yet still want the scalability, flexibility, reliability, and performance of a System z the Power 795 might prove very interesting indeed. And when the POWER8 processor is added to the mix the performance should go off the charts. This is a worthy candidate for enterprise systems consolidation.

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One Response to “Meet the Power 795—the RISC Mainframe”

  1. IBM Builds Out POWER8 Systems | DancingDinosaur Says:

    […] in December, DancingDinosaur referred to the Power System 795 as a RISC mainframe.  It clearly has been superseded by the POWER8 E880 in terms for sheer performance although the […]

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