physical processor, core, logical processor

Processor Groups

https://docs.microsoft.com/en-us/windows/desktop/ProcThread/processor-groups

The 64-bit versions of Windows 7 and Windows Server 2008 R2 and later versions of Windows support more than 64 logical processors on a single computer. This functionality is not available on 32-bit versions of Windows.

Systems with more than one physical processor or systems with physical processors that have multiple cores provide the operating system with multiple logical processors. A logical processor is one logical computing engine from the perspective of the operating system, application or driver. A core is one processor unit, which can consist of one or more logical processors. A physical processor can consist of one or more cores. A physical processor is the same as a processor package, a socket, or a CPU.

Support for systems that have more than 64 logical processors is based on the concept of a processor group, which is a static set of up to 64 logical processors that is treated as a single scheduling entity. Processor groups are numbered starting with 0. Systems with fewer than 64 logical processors always have a single group, Group 0.

How to find the Number of CPU Cores via .NET/C#?

https://stackoverflow.com/questions/1542213/how-to-find-the-number-of-cpu-cores-via-net-c

    [Test]
        public void Test4()
        {
            foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
            {
                Console.WriteLine("Number Of Physical Processors: {0} ", item["NumberOfProcessors"]);
            }

            int coreCount = ;
            foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_Processor").Get())
            {
                coreCount += int.Parse(item["NumberOfCores"].ToString());
            }
            Console.WriteLine("Number Of Cores: {0}", coreCount);

            Console.WriteLine("Number Of Logical Processors: {0}", Environment.ProcessorCount);
        }

Number Of Physical Processors: 1
Number Of Cores: 4
Number Of Logical Processors: 8

powershell查看处理器信息

~\Desktop> Get-WMIObject win32_Processor

Caption           : Intel64 Family  Model  Stepping
DeviceID          : CPU0
Manufacturer      : GenuineIntel
MaxClockSpeed     :
Name              : Intel(R) Core(TM) i7-6820HQ CPU @ .70GHz
SocketDesignation : U3E1

8 logical threads at 4 cores will at a maximum run 4 times faster in parallel?

https://stackoverflow.com/questions/10403201/8-logical-threads-at-4-cores-will-at-a-maximum-run-4-times-faster-in-parallel

A i7-2670QM processor has 4 cores. But it can run 8 threads in parallel. This means that it only has 4 processing units (Cores) but has support in hardware to run 8 threads in parallel. This means that a maximum of four jobs run in on the Cores, if one of the jobs stall due to for example memory access another thread can very fast start executing on the free Core with very little penalty. Read more on Hyper threading. In Reality there are few scenarios where hyper threading gives a large performance gain. More modern processors handle hyper threading better than older processors.

Your benchmark showed that it was CPU bound, i.e. There was little stalls in the pipeline that would have given Hyper Threading an advantage. 50% CPU is correct has the 4 cores are working and the 4 extra are not doing anything. Turn of hyper threading in the BIOS and you will see 100% CPU.

How can my computer have 8 CPUs but only 4 cores? I'm confused about these two concepts.

https://www.quora.com/How-can-my-computer-have-8-CPUs-but-only-4-cores-Im-confused-about-these-two-concepts

Difference between core and processor?

A core is usually the basic computation unit of the CPU - it can run a single program context (or multiple ones if it supports hardware threads such as hyperthreading on Intel CPUs), maintaining the correct program state, registers, and correct execution order, and performing the operations through ALUs. For optimization purposes, a core can also hold on-core caches with copies of frequently used memory chunks.

A CPU may have one or more cores to perform tasks at a given time. These tasks are usually software processes and threads that the OS schedules. Note that the OS may have many threads to run, but the CPU can only run X such tasks at a given time, where X = number cores * number of hardware threads per core. The rest would have to wait for the OS to schedule them whether by preempting currently running tasks or any other means.

In addition to the one or many cores, the CPU will include some interconnect that connects the cores to the outside world, and usually also a large "last-level" shared cache. There are multiple other key elements required to make a CPU work, but their exact locations may differ according to design. You'll need a memory controller to talk to the memory, I/O controllers (display, PCIe, USB, etc..). In the past these elements were outside the CPU, in the complementary "chipset", but most modern design have integrated them into the CPU.

In addition the CPU may have an integrated GPU, and pretty much everything else the designer wanted to keep close for performance, power and manufacturing considerations. CPU design is mostly trending in to what's called system on chip (SoC).

This is a "classic" design, used by most modern general-purpose devices (client PC, servers, and also tablet and smartphones). You can find more elaborate designs, usually in the academy, where the computations is not done in basic "core-like" units.

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