The ability to execute multiple machine instructions in one processor cycle by increasing the number of execution units. The advent of this technology has led to a significant increase in performance, at the same time, there is a certain limit to the growth of the number of executive devices, above which the performance practically stops growing, and the executive devices are idle. A partial solution to this problem is, for example, Hyper-threading technology.
The Harvard architecture differs from the von Neumann architecture in that program code and data are stored in different areas of memory. In such an architecture, many programming methods are impossible (for example, a program cannot change its code during execution; it is impossible to dynamically reallocate memory between program code and data); on the other hand, the Harvard architecture allows more efficient work in the case of limited resources, so it is often used in embedded systems.
The von Neumann architecture has the disadvantage of being sequential. No matter how huge the data array needs to be processed, each of its byte will have to go through the central processor, even if the same operation is required on all the bytes. This effect is called von Neumann bottleneck .
To overcome this shortcoming, processor architectures have been and are being proposed, which are called parallel . Parallel processors are used in supercomputers.
Possible options for parallel architecture are (according to Flynn’s classification):
- SISD – one command stream, one data stream;
- SIMD – one instruction stream, many data streams;
- MISD – many command streams, one data stream;
- MIMD – many command streams, many data streams.
In processors using Hyper-threading technology, each physical processor can store the state of two threads at once, which looks like two logical processors to the operating system. Physically, each of the logical processors has its own set of registers and an interrupt controller, and the rest of the processor elements are common. When a pause occurs in the execution of a thread by one of the logical processors (as a result of a cache miss, branch prediction error, waiting for the result of the previous instruction), then control is transferred to the thread in another logical processor. Thus, while one process is waiting for, for example, data from memory, the computing resources of the physical processor are used to process another process.
Complex instruction set computer – calculations with a complex set of commands. A processor architecture based on a sophisticated instruction set. Typical representatives of CISC are microprocessors of the x86 family (although for many years these processors have been CISC only by an external instruction system: at the beginning of the execution process, complex instructions are broken down into simpler micro-operations (MOS) executed by the RISC core).
Reduced instruction set computer – calculations with a simplified set of instructions (in the literature, the word reduced is often mistakenly translated as “reduced”). The architecture of processors, built on the basis of a simplified instruction set, is characterized by the presence of fixed-length instructions, a large number of registers, register-to-register operations, and the absence of indirect addressing. The concept of RISC was developed by John Cock of IBM Research, the name was coined by David Patterson.
The simplification of the instruction set is intended to reduce the pipeline, which avoids delays in the operations of conditional and unconditional jumps. A homogeneous set of registers simplifies the work of the compiler when optimizing the executable program code. In addition, RISC processors are characterized by lower power consumption and heat dissipation.
Among the first implementations of this architecture were MIPS, PowerPC, SPARC, Alpha, PA-RISC processors. ARM processors are widely used in mobile devices.
Minimum instruction set computer – calculations with a minimum set of commands. Further development of the ideas of the team of Chuck Moore, who believes that the principle of simplicity, which was originally for RISC processors, has faded into the background too quickly. In the heat of the fight for maximum performance, RISC has caught up and surpassed many CISC processors in complexity. The MISC architecture is based on a stack computing model with a limited number of instructions (approximately 20-30 instructions).
Very long instruction word – an extra long command word. The architecture of processors with explicitly expressed parallelism of calculations incorporated into the processor instruction set. They are the basis for the EPIC architecture. The key difference from superscalar CISC processors is that for them, a part of the processor (scheduler) is involved in loading the execution devices, which takes a fairly short time, while the compiler is responsible for loading the computing devices for the VLIW processor, which takes much more time. (the quality of the download and, accordingly, the performance should theoretically be higher). An example of a VLIW processor is the Intel Itanium.
M.P. – a complex multilayer printed circuit board, which is the basis for building a computing system (computer). In some complex electronic devices and devices (communicator, tablet), the main (largest, most significant) device board can also be called the motherboard or system board.
As the main (non-removable) parts, the motherboard has a processor socket, chipset chips, boot ROM, bus controllers and I / O interfaces and peripherals. RAM in the form of memory modules are installed in specially designed slots; Expansion cards are installed in the expansion slots.
An additional cooling system and peripherals are mounted inside the chassis, together forming a computer system unit.
Back in the middle of the last century, computer boards contained up to two hundred microcircuits. The motherboard, which forms the basis of the computing system of a modern general-purpose computer, contains two main large microcircuits:
The northbridge is a system controller, which is one of the elements of the motherboard chipset, responsible for working with random access memory (RAM), video adapter and processor (CPU). The northbridge is responsible for the frequency of the system bus, the type of RAM and its maximum possible amount. One of the main functions of the north bridge is to ensure the interaction between the motherboard and the processor, as well as determining the speed of operation. Part of the northbridge in many modern motherboards is the integrated video adapter. Thus, the functional feature of the north bridge is also the control of the video adapter bus and its speed. Also, the northbridge connects all of the above devices with the southbridge.
The Southbridge is a functional controller known as the I/O Controller or ICH (In/Out Controller Hub). Responsible for the so-called “slow” operations, which include working out the interaction between the IDE, SATA, USB, LAN, Embeded Audio interfaces and the northbridge of the system, which, in turn, is directly connected to the processor and other important components, such as RAM or video subsystem. Also, the south bridge is responsible for processing data on the PCI, PCIe buses. Also, the south bridge is responsible for the SM bus (which is used to control the fans on the board), DMA controller, IRQ controller, system clock, BIOS, power supply systems.
Chipset microcircuits determine the operation capabilities of external devices installed in the computer system processor (video card, hard drive, etc.)
Motherboard form factor – a standard that determines the size of the motherboard for a computer, where it is attached to the chassis; the location of the bus interfaces, I/O ports, processor socket, RAM slots on it, as well as the type of connector for connecting the power supply.
The form factor (like any other standards) is advisory in nature. The form factor specification defines required and optional components. However, the vast majority of manufacturers prefer to comply with the specification, since the price of compliance with existing standards is the compatibility of the motherboard and standardized equipment (peripherals, expansion cards) from other manufacturers (which is key to reducing the cost of ownership).
– Modern and widely used formats: ATX; microATX.
– Embedded formats: Mini-ITX, MicroBTX.
There are motherboards that do not match any of the existing form factors. This is a fundamental decision of the manufacturer, due to the desire to create a “brand” incompatible with existing products on the market and exclusively produce peripheral devices and accessories for it.