IBM Systems Magazine, Mainframe - May/June 2015 - 43

The z13 core consists of
multiple processing units and
stages. The front end consists
of the "branch prediction" (IFB)
unit, the "instruction fetching
and caching" (ICM) unit and
the "instruction buffer, queuing
and decoding" unit (IDU) that
process instructions in program
order. The instruction issue
unit (ISU) and the execution
units process instructions out of
program order.
Figure 1 (page 44) shows a
typical snapshot of thread 0
and thread 1 execution in these
pipeline stages during SMT2
mode. In a given cycle IFB can
predict instruction branch
directions and targets for just one
thread. In the next cycle it can
switch to provide predictions for
the other thread. Similarly, in a
given cycle the instruction for
just one thread is accessed from
the instruction cache and in the
next cycle instruction fetching
can switch to the other thread.
The decoding and dispatching
pipeline stages also operate on
one thread at a time and these
pipeline stages can alternate
between threads each cycle.
The branch prediction history
structures and instruction cache
are shared by both threads,
while the instruction buffer
and queue in the IDU are
statically partitioned into two
halves: top half dedicated
to thread 0 and bottom half
dedicated to thread 1.
The "register mapping and
instruction wake-up and issue"
unit (ISU) is key to enabling
both out of order processing
and multithreaded operations.
Although the register mapping
function, which dynamically
calculates register renaming
assignments to allow out of
order operations, works on one
thread at a time, the instruction
wake-up and issue logic operates

on both threads concurrently.
As a result, instructions from
both threads can be issued
concurrently into the execution
units: the load/store unit that
contains the data cache (LSU),
the fixed point unit (FXU), the

floating point unit (BFU), the
decimal floating point unit (DFU)
and the SIMD unit.
For example, a load instruction
from thread 0 can issue to
load/store unit 1 and a store
instruction from thread 1

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ibmsystemsmag.com MAY/JUNE 2015 // 43


http://ibmsystemsmag.webex.com http://www.ibmsystemsmag.com

IBM Systems Magazine, Mainframe - May/June 2015

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe - May/June 2015

Table of Contents
IBM Perspective: A mainframe built for Generation Z
Editor's Desk: Optimistic future
Partner PoV: Now is the time for multifactor authentication
Infographic: Myths, exaggerations and uncomfortable truths
Currents: TCO for an IBM z13 cloud is lower than an x86 or public cloud, according to an IBM study
R&D: IBM Research is working to better diagnose osteoporosis -- and make computing more economical
Cover Story: Mastering the Mainframe: IBM contest connects millennials to the mainframe and potential employers
Feature: The Millennial Career Guidebook: Six groups and resources to help mainframers starting their careers
Feature: Mainframe Within Reach: IBM provides a rich set of solutions designed to help new mainframe programmers
Tech Showcase: IBM X-Force report reveals challenges and strategies to succeed in the new computing environment
Tech Corner: New IBM z13 chip improves throughput and analytics performance
Solutions: ReACT V4.0; Ivory Service Architect V4.6
Stop Run: Running and fencing keep IBMer active
Reference Point - Global Events, Education, Resources for Mainframe
2015 Mainframe Solutions Edition Product Index
Linux on z E-book
IBM Systems Magazine, Mainframe - May/June 2015 - Intro
IBM Systems Magazine, Mainframe - May/June 2015 - Cover1
IBM Systems Magazine, Mainframe - May/June 2015 - Cover2
IBM Systems Magazine, Mainframe - May/June 2015 - 1
IBM Systems Magazine, Mainframe - May/June 2015 - Table of Contents
IBM Systems Magazine, Mainframe - May/June 2015 - 3
IBM Systems Magazine, Mainframe - May/June 2015 - 4
IBM Systems Magazine, Mainframe - May/June 2015 - IBM Perspective: A mainframe built for Generation Z
IBM Systems Magazine, Mainframe - May/June 2015 - Editor's Desk: Optimistic future
IBM Systems Magazine, Mainframe - May/June 2015 - 7
IBM Systems Magazine, Mainframe - May/June 2015 - Partner PoV: Now is the time for multifactor authentication
IBM Systems Magazine, Mainframe - May/June 2015 - 9
IBM Systems Magazine, Mainframe - May/June 2015 - Infographic: Myths, exaggerations and uncomfortable truths
IBM Systems Magazine, Mainframe - May/June 2015 - Currents: TCO for an IBM z13 cloud is lower than an x86 or public cloud, according to an IBM study
IBM Systems Magazine, Mainframe - May/June 2015 - 12
IBM Systems Magazine, Mainframe - May/June 2015 - 13
IBM Systems Magazine, Mainframe - May/June 2015 - 14
IBM Systems Magazine, Mainframe - May/June 2015 - 15
IBM Systems Magazine, Mainframe - May/June 2015 - R&D: IBM Research is working to better diagnose osteoporosis -- and make computing more economical
IBM Systems Magazine, Mainframe - May/June 2015 - 17
IBM Systems Magazine, Mainframe - May/June 2015 - 18
IBM Systems Magazine, Mainframe - May/June 2015 - 19
IBM Systems Magazine, Mainframe - May/June 2015 - Cover Story: Mastering the Mainframe: IBM contest connects millennials to the mainframe and potential employers
IBM Systems Magazine, Mainframe - May/June 2015 - 21
IBM Systems Magazine, Mainframe - May/June 2015 - 22
IBM Systems Magazine, Mainframe - May/June 2015 - 23
IBM Systems Magazine, Mainframe - May/June 2015 - Feature: The Millennial Career Guidebook: Six groups and resources to help mainframers starting their careers
IBM Systems Magazine, Mainframe - May/June 2015 - 25
IBM Systems Magazine, Mainframe - May/June 2015 - 26
IBM Systems Magazine, Mainframe - May/June 2015 - 27
IBM Systems Magazine, Mainframe - May/June 2015 - 28
IBM Systems Magazine, Mainframe - May/June 2015 - 29
IBM Systems Magazine, Mainframe - May/June 2015 - Feature: Mainframe Within Reach: IBM provides a rich set of solutions designed to help new mainframe programmers
IBM Systems Magazine, Mainframe - May/June 2015 - 31
IBM Systems Magazine, Mainframe - May/June 2015 - 32
IBM Systems Magazine, Mainframe - May/June 2015 - Tech Showcase: IBM X-Force report reveals challenges and strategies to succeed in the new computing environment
IBM Systems Magazine, Mainframe - May/June 2015 - 34
IBM Systems Magazine, Mainframe - May/June 2015 - 35
IBM Systems Magazine, Mainframe - May/June 2015 - 36
IBM Systems Magazine, Mainframe - May/June 2015 - 37
IBM Systems Magazine, Mainframe - May/June 2015 - 38
IBM Systems Magazine, Mainframe - May/June 2015 - 39
IBM Systems Magazine, Mainframe - May/June 2015 - 40
IBM Systems Magazine, Mainframe - May/June 2015 - 41
IBM Systems Magazine, Mainframe - May/June 2015 - Tech Corner: New IBM z13 chip improves throughput and analytics performance
IBM Systems Magazine, Mainframe - May/June 2015 - 43
IBM Systems Magazine, Mainframe - May/June 2015 - 44
IBM Systems Magazine, Mainframe - May/June 2015 - 45
IBM Systems Magazine, Mainframe - May/June 2015 - 46
IBM Systems Magazine, Mainframe - May/June 2015 - Solutions: ReACT V4.0; Ivory Service Architect V4.6
IBM Systems Magazine, Mainframe - May/June 2015 - Stop Run: Running and fencing keep IBMer active
IBM Systems Magazine, Mainframe - May/June 2015 - Cover3
IBM Systems Magazine, Mainframe - May/June 2015 - Cover4
IBM Systems Magazine, Mainframe - May/June 2015 - Reference Point - Global Events, Education, Resources for Mainframe
IBM Systems Magazine, Mainframe - May/June 2015 - RF2
IBM Systems Magazine, Mainframe - May/June 2015 - Linux on z E-book
IBM Systems Magazine, Mainframe - May/June 2015 - L2
IBM Systems Magazine, Mainframe - May/June 2015 - L3
IBM Systems Magazine, Mainframe - May/June 2015 - L4
IBM Systems Magazine, Mainframe - May/June 2015 - L5
IBM Systems Magazine, Mainframe - May/June 2015 - L6
IBM Systems Magazine, Mainframe - May/June 2015 - L7
IBM Systems Magazine, Mainframe - May/June 2015 - L8
IBM Systems Magazine, Mainframe - May/June 2015 - L9
IBM Systems Magazine, Mainframe - May/June 2015 - L10
IBM Systems Magazine, Mainframe - May/June 2015 - L11
IBM Systems Magazine, Mainframe - May/June 2015 - L12
IBM Systems Magazine, Mainframe - May/June 2015 - L13
IBM Systems Magazine, Mainframe - May/June 2015 - L14
IBM Systems Magazine, Mainframe - May/June 2015 - L15
IBM Systems Magazine, Mainframe - May/June 2015 - L16
IBM Systems Magazine, Mainframe - May/June 2015 - L17
IBM Systems Magazine, Mainframe - May/June 2015 - L18
IBM Systems Magazine, Mainframe - May/June 2015 - L19
IBM Systems Magazine, Mainframe - May/June 2015 - L20
IBM Systems Magazine, Mainframe - May/June 2015 - L21
IBM Systems Magazine, Mainframe - May/June 2015 - 2015 Mainframe Solutions Edition Product Index
IBM Systems Magazine, Mainframe - May/June 2015 - SE2
IBM Systems Magazine, Mainframe - May/June 2015 - SE3
IBM Systems Magazine, Mainframe - May/June 2015 - SE4
IBM Systems Magazine, Mainframe - May/June 2015 - SE5
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