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, 7
ADI 10
HLT
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
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•
•
•
Cache
Control logic
Buses
Branch predictors
Performance
• Intel claims up to 30% increase
• Many reviews have different results
• Test your own
Benchmarking
•
•
•
•
•
•
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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 BIOS
2. 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
PCMark
non-HT
Result 1
HT
Result 2
non-HT
Result 2
4861
4329
4833
4274
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
PCMarks
Benchmarking Reults
HT result 1
Non-HT result 1
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
2466.6
1565.8
2729.7
1599.8
MB/s
2.0
2.2
2.1
2.4
KB/s
91.1
90.8
84.8
81.3
MB/s
2827.2
2819.9
2814.0
2814.9
KB/s
5.6
5.5
5.6
5.4
WMV Video Compression
56.2
49.6
52.0
46.4
FPS
DivX Video Compression
63.3
55.2
62.9
51.7
FPS
180.5
173.2
176.0
178.6
FPS
File Compression
Virus Scanning
Grammar Check
File Decryption
Audio Conversion
Web Page Rendering
Physics Calculation and 3D
HT result 2 Non-HT result2
Pages/s
Tom’s video
Conclusion
• Benefits Home PC user
• Multitaking performance