Hyper Threading

By Jeffrey Rodriguez

What is Hyper Threading?

• Intel’s implementation of Symmetric Multithreading (SMT)

• Two threads executing concurrently in one processor

History of HT

• Codenamed ‘Jackson’ technology

• First unveiled at Intel Developer Forum in fall 2001.

• Not first company with SMT technology

Original SMT

• Compaq develops SMT in 1999

• Unveils at Microprocessor Forum, San Jose, CA

• Project is canceled before its release

HT takes mainstream

• Originally introduced on Xeon line of processors

• Brought to desktop PC with 3.06 GHz Pentium 4

• Grown to 2.8 GHz – 3.8 GHz range P4

http://www6.tomshardware.com/cpu/20021202/images/image1.gif

A basic CPU

Sample program:

MVI A, 7ADI 10HLT

Single Thread

• Single threaded CPU

• Multiple threads in RAM

• One at a time

http://arstechnica.com/paedia/images/figure-1.html

Multiple CPUs

• Dual CPUs

• Single threaded

• Double output

• Half efficiency

http://arstechnica.com/paedia/images/figure-2.html

Super Threading

• Multiple threads

• One thread per pipeline

• Increased efficiency

http://arstechnica.com/paedia/images/figure-3.html

Hyper Threading

• Multiple threads

• Two threads per pipeline

• Maximum efficiency

http://arstechnica.com/paedia/images/figure-4.html

Hyper Threading

• Simulates two processors

• Two architectural states

• OS can schedule process on each ‘logical’ processor

Logical Processors

• Duplicated components• general purpose registers• control registers • the program counter• the advanced programmable interrupt

controller (APIC)• machine state registers

Logical Processors

• Shared components• Cache• Control logic• Buses• Branch predictors

Performance

• Intel claims up to 30% increase

• Many reviews have different results

• Test your own

Benchmarking• CPU – Intel 3.2 GHz P4 w/HT• MB – Asus P4C800 E-Dlx Rev. 1.xx• RAM – 4x512 MB Corsair• Video – Asus ATI Radeon 9800XT• Sound – Audigy 2 ZS Platinum• HD – 200 GB SATA, 120 GB IDE, 80 GB IDE• OS – Microsoft Windows XP Pro SP2• PCMark 2004 Version 1.2

Benchmarking

1. Disabled HT in BIOS2. Killed all startup processes

• 23 running while testing

3. Ran test software

• Repeated to enable HT• Each test run twice

Benchmarking Results

 

HT Result 1

non-HT Result 1

HT Result 2

non-HT Result 2  

PCMark 4861 4329 4833 4274 PCMarks

CPU 4804.0 4110.0 4704.0 3969.0  

Memory 4639.0 4518.0 4556.0 4558.0  

Graphics 4430.0 4454.0 4440.0 4406.0  

HDD 3851.0 3182.0 3443.0 3428.0  

Benchmarking ReultsHT result 1 Non-HT result 1 HT result 2 Non-HT result2

File Compression 5.5 4.1 5.4 4.0 MB/s

File Encryption 51.8 45.6 51.1 44.3 MB/s

File Decompression 38.0 27.1 37.8 27.5 MB/s

Image Processing 14.3 13.2 14.6 13.4 MPixels/s

Virus Scanning 2466.6 1565.8 2729.7 1599.8 MB/s

Grammar Check 2.0 2.2 2.1 2.4 KB/s

File Decryption 91.1 90.8 84.8 81.3 MB/s

Audio Conversion 2827.2 2819.9 2814.0 2814.9 KB/s

Web Page Rendering 5.6 5.5 5.6 5.4 Pages/s

WMV Video Compression 56.2 49.6 52.0 46.4 FPS

DivX Video Compression 63.3 55.2 62.9 51.7 FPS

Physics Calculation and 3D 180.5 173.2 176.0 178.6 FPS

Tom’s video

Conclusion

• Benefits Home PC user

• Multitaking performance