Hardware Reference
In-Depth Information
SSE3.
SSE4 (also called HD Boost by Intel) was introduced in January 2008 in versions of the Intel Core 2
processors (SSE4.1) and was later updated in November 2008 in the Core i7 processors (SSE4.2).
SSE4 consists of 54 total instructions, with a subset of 47 instructions comprising SSE4.1, and the
full 54 instructions in SSE4.2.
Advanced vector extensions (AVX) was introduced in January 2011 in the second-general Core i-
series “Sandy Bridge” processors and is also supported by AMD's new “Bulldozer” processor
family. AVX is a new 256-bit instruction set extension to SSE, comprising 12 new instructions. AVX
helps floating-point intensive applications such as image and A/V processing, scientific simulations,
financial analytics, and 3D modeling and analysis to perform better. AVX is supported on Windows 7
SP1, Windows Server 2008 R2 SP1, and Linux kernel version 2.6.30 and higher. For AVX support
on virtual machines running on Windows Server R2, see
http://support.microsoft.com/kb/2517374
for
a hotfix.
For more information about AVX, see
http://software.intel.com/en-us/avx/
. Although AMD has
adopted Intel SSE3 and earlier instructions in the past, instead of adopting SSE4, AMD has created a
different set of only four instructions it calls SSE4a. Although AMD had planned to develop its own
instruction set called SSE5 and release it as part of its new “Bulldozer” processor architecture, it
decided to shelve SSE5 and create new instruction sets that use coding compatible with AVX. The
new instruction sets include
•
XOP
—Integer vector instructions
•
FMA4
—Floating point instructions
•
CVT16
—Half-precision floating point conversion
3DNow!
3DNow! technology was originally introduced as AMD's alternative to the SSE instructions in the
Intel processors. It included three generations: 3D Now!, Enhanced 3D Now!, and Professional 3D
Now! (which added full support for SSE). AMD announced in August 2010 that it was dropping
support for 3D Now!-specific instructions in upcoming processors.
For more information about 3D Now!, see “3D Now” in Chapter 3 of
Upgrading and Repairing PCs
,
19
th
Edition, which is supplied on the disc packaged with this topic.
Dynamic Execution
First used in the P6 (or sixth-generation) processors, dynamic execution enables the processor to
execute more instructions in parallel, so tasks are completed more quickly. This technology
innovation is composed of three main elements:
•
Multiple branch prediction
—Predicts the flow of the program through several branches
•
Dataflow analysis
—Schedules instructions to be executed when ready, independent of their
order in the original program
•
Speculative execution
—Increases the rate of execution by looking ahead of the program
counter and executing instructions that are likely to be necessary
Branch Prediction
Branch prediction
is a feature formerly found only in high-end mainframe processors. It enables the
