1/26/2024 0 Comments Cpu transistor functionThe terms threads and processors are commonly used to mean different things in hardware and software contexts. The modules interface with the CPU fabric rather than the cores interfacing directly. In these processors, two cores share a large L2 cache. Intel Atom processors also have the concept of CPU modules. Operating systems manage a large number of software threads and perform context switches to pick which software thread is active on a given hardware thread at a given point in time. There are two types of threads: hardware threads and software threads. The additional throughput and performance can increase the overall power draw, but the wall power increase is small compared to the potential performance upside. SMT is typically a very power-efficient technique. Running multiple threads on a given core can reduce the per thread performance while increasing the overall throughput. This is particularly true when a thread is stalled for some reason (such as when it is waiting for a response from memory). SMT attempts to take advantage of the fact that a single thread of execution on a core does not, on many workloads, make use of all the resources available in the core. These technologies were introduced in Intel CPUs in 2002. This technique has multiple names, including simultaneous multithreading (SMT) and Hyper-Threading Technology (HT). These are also known as logical processors. Individual cores can support multiple hardware threads of execution. Others may add substantial vector throughput while sacrificing the ability to handle complex control flow. Some cores, for example, may sacrifice floating point performance in order to reduce area and cost. As a result, more specialized cores are also possible. However, achieving highest performance across a wide range of workloads has associated costs. Traditional server CPUs, such as those found in Intel’s Xeon E5 systems, are built using general purpose cores optimized to provide good performance across a wide range of workloads. Table 2-1 provides some high-level definitions for the primary CPU components.įull size table Threads, Cores, and Modules The boxes with a dashed outline are optionally included on the CPU Silicon die, whereas the others are now almost always integrated into the same die as the cores. Figure 2-1 shows an example of such a system. The main components of a modern CPU are the cores that perform the computation, I/O for sending and receiving the data that is required for the computation, memory controllers, and support infrastructure allowing these other pieces to efficiently communicate with each other. Typical multi-core server CPUs follow a common high-level architecture in order to efficiently provide compute agents with the data that they require. On the other hand, a cold storage deployment Footnote 1-where a large number of hard drives hold data that is very infrequently accessed over a connection with much lower bandwidth-may require much lower CPU performance in order to suit the needs of the end user. In such systems, it is desirable to maximize per node performance in order to reduce the communication subsystem costs and dependency. These communication networks can be very expensive and hence contribute significantly to data center TCO. For example, many high performance computing (HPC) workloads are very sensitive to scaling and cross-node communication. Different workloads have different sweet spots. Because the CPU plays a central role in information processing, matching the CPU with the right amount of performance/capabilities with the other data center infrastructure is critical to achieving the best TCO. In more recent years, highly scalable interconnects have been developed inside CPUs in order to facilitate the scaling of the number of cores.Ī less widely known goal of CPU design is optimization for total cost of ownership (TCO) amortization. Caches, main memory, and hard drives provide a hierarchical mechanism for storing data with varied capacity, bandwidth, and latency tradeoffs. However, no core is complete without an effective support system to provide the core with the data it needs to execute. Over the years, server CPU core design has significantly evolved to provide high performance and energy-efficient execution of workloads.
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