Hyperthread CPU's question
Discussion
scared but happy said:
Am I right in assuming that it is just one CPU that emulates two? So in fact you are running a virtual CPU?
More or less. Every CPU has multiple execution units (like the floating point unit, integer unit etc). Hyper threading basically allows more than one unit to be used at the same time. To allow access to this feature 2 CPU's are presented. You can't always use all the units in parallel which is why hyper threading only gives a max of 30% more go.
All a bit simplified above and there can be issues with it, but for games and video/audio encoding it's almost always a good thing to use. Any apps that use lots of memory...that's a different story....
A microprocessor has various resources. You have things like a program counter that maintains the position that you're currently at in the program, and then things like adders and multipliers, that actually do the sums that are described in the program. You need at least one of each of these things to be able to run a program.
Multithreaded programs, are like two separate programs, which talk to each other in order to get the whole job done.
Previously your PC has had the ability to switch between these programs on the fly, but critically if your program was instantaneously doing an add, then the multiplier would be idle.
Multiprocessor systems have been possible for a long time, where each thread runs on a different processor. Some of the AMD family of Micros, now offer a monolitic solution where two processors are on the same piece of silicon, and can run the two threads, or programs symultaneously.
Intel never believed in the idea of interprocessor communication, which also has been around a long time. When AMD went for a similar sounding, but completely different approach to multiprocessor computing, HyperTransport, Intel realised that they were behind the curve.
They were unable to come up with a similar, competing solution, and so they decided to devise HyperThreading to keep customers happy. Hyperthreading essentially allows two or (potentially) more programs to execute symultaneously, but not all the time.
Essentially individual resources like multipliers and adders are pipelined. This means that if one program wants to do an add, and the other wants to do a multiply, then these operations can happen symultaneously. If two programs want to do an add, at the same time, then one has to wait.
Overall when intel move across to a solution that uses interprocessor communication, they will again have the advantage, because they will likely adopt a solution which uses both "Hyperthreading" and "Hypertransport".
Intel also have a deeper technological advantage, in that they have the direct ability to produce 90nm and 45nm semiconductors, which many semiconductor companies do not. This stems from their ability to produce SiGe implants under the gate area of their transistors. This capability improves the electron mobility of their transistors, and reduces power consumption for a given performance level.
Multithreaded programs, are like two separate programs, which talk to each other in order to get the whole job done.
Previously your PC has had the ability to switch between these programs on the fly, but critically if your program was instantaneously doing an add, then the multiplier would be idle.
Multiprocessor systems have been possible for a long time, where each thread runs on a different processor. Some of the AMD family of Micros, now offer a monolitic solution where two processors are on the same piece of silicon, and can run the two threads, or programs symultaneously.
Intel never believed in the idea of interprocessor communication, which also has been around a long time. When AMD went for a similar sounding, but completely different approach to multiprocessor computing, HyperTransport, Intel realised that they were behind the curve.
They were unable to come up with a similar, competing solution, and so they decided to devise HyperThreading to keep customers happy. Hyperthreading essentially allows two or (potentially) more programs to execute symultaneously, but not all the time.
Essentially individual resources like multipliers and adders are pipelined. This means that if one program wants to do an add, and the other wants to do a multiply, then these operations can happen symultaneously. If two programs want to do an add, at the same time, then one has to wait.
Overall when intel move across to a solution that uses interprocessor communication, they will again have the advantage, because they will likely adopt a solution which uses both "Hyperthreading" and "Hypertransport".
Intel also have a deeper technological advantage, in that they have the direct ability to produce 90nm and 45nm semiconductors, which many semiconductor companies do not. This stems from their ability to produce SiGe implants under the gate area of their transistors. This capability improves the electron mobility of their transistors, and reduces power consumption for a given performance level.
dilbert...
Pentium-D's are actually dual core (two processors on one piece of silicon). Intel have already instituted your prognostication with the Extreme (I use one at home). The Pentium Extreme is a dual core processor. Each processor core, additionally, has hyperthreading. So, for the cost of one processor 775 socket, I get 4 virtual processors. It does a bang up job on video rendering I can tell you...
ErnestM
Pentium-D's are actually dual core (two processors on one piece of silicon). Intel have already instituted your prognostication with the Extreme (I use one at home). The Pentium Extreme is a dual core processor. Each processor core, additionally, has hyperthreading. So, for the cost of one processor 775 socket, I get 4 virtual processors. It does a bang up job on video rendering I can tell you...
ErnestM
HyperTransport is nothing to do with multi threading processors 
it's a bus technology for connecting two devices together such as a north and south bridge on a chipset.
Also Intel had HyperThreading about a year before AMD released the dual core CPUs, it wasn't like it was their last minute solution. It was more a stepping stone to multicore CPUs. Intel is currently on it's second genreation of Dual Core CPUs, the Pentuim D8xx were first and now we have the B9xx.
BTW I have an AMD 64 system so i'm not some kind of Intel fanatic
it's a bus technology for connecting two devices together such as a north and south bridge on a chipset. Also Intel had HyperThreading about a year before AMD released the dual core CPUs, it wasn't like it was their last minute solution. It was more a stepping stone to multicore CPUs. Intel is currently on it's second genreation of Dual Core CPUs, the Pentuim D8xx were first and now we have the B9xx.
BTW I have an AMD 64 system so i'm not some kind of Intel fanatic
mr_yogi said:
HyperTransport is nothing to do with multi threading processors
Also Intel had HyperThreading about a year before AMD released the dual core CPUs, it wasn't like it was their last minute solution. It was more a stepping stone to multicore CPUs. Intel is currently on it's second genreation of Dual Core CPUs, the Pentuim D8xx were first and now we have the B9xx.
BTW I have an AMD 64 system so i'm not some kind of Intel fanatic
That'll be why senior tech exec's left intel in frustration then? Intel went for their hyperthreading solution, and AMD went for HyperTransport. That's why the particular tech exec that I have I mind left Intel. He tried to convince them that sales would be hit if they didn't opt for a multiprocessor solution that made use of interprocessor communication. Intel disagreed with him, he was right, and sales for Intel fell.
I also point out that that I never said that HyperTransport was exclsively to do with multi threading processors. In fact, it sits with a variety of industrial and military standards that have been in existance for a considerable period of time.
It's useful and positive to me, to know, know that the "Intel Extreme" architecture buzz-word is essentially dual core. Not being "some kind of intel fanatic" I don't follow what they do with any great regularity. I guess it must have been some time ago now since all this happened.
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