Paul Gogue
Unit 2
Hyper-Threading
NT1110

Introduction: Hyper-threading or HT technology is used by some Intel microprocessor's which allows a single microprocessor to act like two seperate processors to the operating system and the application programs that use it. Hyper-threading enables the "core" processor to execute two concurrent threads of instruction sent by the OS. This simultaneous multi-thread implementation (SMT) is used to improve the parellization of computation, which means more work to be done by the processor during each clock cycle. To the OS the HT micro-processors appear to be seperate processors, because the HT technology uses two virtual core's for every physical core.

A Multi-core processor is a single computing component with two or more independent core's, which usually means two or more CPUs/core's working together on the same chip. Multi-core technolgy adds physical CPUs/core's which are the units that read and execute program instructions, adding multiple core's enables multiple instructions to be executed. The multiple core's improves performance, reduces power consumption, an more efficient simultaneous processing of multiple tasks amenable to parellel computing.

Summary: Hyper threading stopped with P4 because there wasn't enough spare capacity in the core for the second thread. Each thread gets less cache to work with, and if they simultaneously need memory or the same resources, switching back and forth between them can cause performance problems. Though HT stopped with P4, the i7 is making use of the technolgy an has also been designed with more capacity.

Mulit-core processor technology has all the advantages vs HT technology. The HT technology is not a symmetric multi process, which means theres only one processor that pretends it consists of two. Which doesn't enable it to perform multi-tasking to its full extent, where the multi-core tech actually adds a physical over the HT virtual method. This allows for multi-tasking performance to be greatly enhanced. Though multi0core is the superior newer model CPU's have been using both HT and multi-core, like the i7. The reason is for even greater enhanced multi-tasking performance, by adding the physical cores you would have two virtual for each.

Windows XP doesnt support more than one physical processor, so the obvious choice would be HT. XP has trouble identifying the number and type of processors. It can identify the physical or logical processors but has trouble with multi-core processors (there's a hotfix). Win 7 on the other hand works better with a multi-core processor, but is optimized for hyper-threading.

Conclusion: The conclusion I've drawn from my research is, multi-core processors are more effective than the HT tech. Multi-core allows for better performance due to the fact that adding the physical cores is more effective than the HT method of one core pretending to be two. Though the multi-core tech is the better of the two, working them both together far exceeds either alone.

Referrences: http://www.dailytech.com/Windows+7+to+Offer+Better+HyperThreading+Support/article15150.htm https://en.wikipedia.org/wiki/Hyper-threading https://en.wikipedia.org/wiki/Multi-core_processor http://www.yale.edu/pclt/PCHW/Hyperthreading.htm http://support.microsoft.com/kb/810231 http://www.tomshardware.com/news/windows-hyperthreading-intel-nehalem-atom,7831.html