Power Supply Unit

A power supply unit is a device that converts AC voltage to DC voltage for connecting a computer or a computer server.

Power supplies for desktops provide output ranging from 300W to more than 1,000W.

Application

One of the main functions of a power supply is to convert the current from AC to DC (rectification). Besides driving the computer, the power supply also performs the function of stabilization and protection against minor disturbances in the supply voltage circuit.

Motherboard Compatibility

The power supply can be:

With soldered wires

Modular

If the power supply with soldered wires does not adapt to the motherboard, you can use an adapter.

A modular power supply is a more expensive option than a standard power supply, but it has a lot of great advantages:

• It is possible to change and use the cable that fits your motherboard without adapters.
• No extra wires are hanging; they do not need to be hidden and tied up. This positively affects the air circulation inside the case.
• You can choose the length of the cables.
• Less unnecessary cables reduce the amount of dust in the PC case.

The form factor of commercially available power supplies

1 - The classic ATX standard power supply. It is the most common typical power supply. Dimensions: Height 86mm, Width 150mm, Depth 140mm.

2 - SFX power supply. It is suitable for small computers. SFX can be installed with a special adapter in the ATX case. Dimensions: Height 51,5mm, Width 125mm, Depth 100mm.

3 - TFX power supply. It can be used in small height or special design chassis. Dimensions: Height 65 mm, Width 85 mm, Depth 175 mm.

4 - Flex-ATX power supply. It is a solution for compact desktop systems and servers. Dimensions: Height 40,5 mm, Width 81,5 mm, Depth 150 mm.

5 - Laptop power supply.

What's inside

AC/220 means alternating current 220 volts. It is the connector for the power supply.

Many electrical devices in homes, offices are constantly turning on and off. This can cause voltage fluctuations in the mains. The power supply balances out the input voltage.

The power supply includes input filters. These are capacitors that absorb voltage surges.

The power supply converts the AC input voltage into a DC voltage of 12V, 5V, and 3.3V.

A kind of power supply

1 - Rectifier bridge;

2 - Capacitors;

3 - Pulse width modulator;

4 - Step-down transformer to 12V;

4.2 - Step-down transformer to 5V;

5 - Aluminum heatsink for low voltage diodes.

Output connectors

Each output connector includes two wires: for example, one for the +5 V and a second ground wire for potential equalization. These two wires make a loop: from the power supply to the consumer device and then back to the power supply.

The main connector is a 24-pin ATX12V. This connector provides the main power with several pins of different voltages and several special pins. One of the special connectors is the "+5 standby" output.  This connector provides standby power for the computer. Standby power is required for the motherboard to stay active.

Most power supplies also have an 8-pin connector for the motherboard with two +12V lines and at least one 6-pin or 8-pin PCI Express connector. The difference between the 6-pin and 8-pin PCI Express connectors is two extra ground wires. It allows for more current for high-powered graphics cards.

The Serial ATA (SATA) connector is used to supply power to hard drives, solid-state drives, and DVD drives.

The AMP Mate-N-LOK power connector supplies one +12V, +5V output each, and two ground wires.

Random Access Memory

Random Access Memory (RAM) is the part of a computer memory system that stores executable machine code, input data, output data, and intermediate data processed by the processor.

RAM is a volatile part of the computer memory system. The data contained in semiconductor RAM is accessible and stored only when voltage is applied to the memory modules. If the RAM power is turned off, the stored information in the RAM will be lost.

Types of RAM

There are two types of RAM:

• (SRAM) Static memory is an array of triggers.

A trigger is a device that can be in one of two stable states. It switches from one state to another under the influence of an input signal. The active parts of triggers are transistors and logic gates. A group of transistors and logic gates in a trigger occupies more space than a dynamic memory (DRAM) cell.

Static memory is faster than dynamic memory. Therefore, this type of memory is used to build a cache memory inside the microprocessor.

• (DRAM) Dynamic memory consists of an array of capacitors.

A capacitor is a device for accumulating an electric field charge.

A transistor is a semiconductor component that can drive current in the output circuit from a small input signal. It makes it possible to use it to amplify, switch, and convert electrical signals.

Dynamic memory gets its name from the fact that the capacitor charge gradually decreases over time. A single-bit memory cell consists of a capacitor and a transistor. The capacitor can be charged to a high voltage (logic 1) or a low voltage (logic 0). The transistor acts as a key that connects the capacitor to the control circuitry. The control circuitry allows the capacitor charge state to be read or changed. The density of dynamic memory is higher than static memory. This allows more memory cells to be placed on the silicon chip area of dynamic memory modules.

DRAM is slower than SRAM. This is because a capacitor needs to be charged or discharged to change its state. Recharging the capacitor takes more time than switching the trigger.  To avoid losing the contents of the memory, the capacitor charge value is periodically regenerated through a time called the regeneration cycle. The regeneration procedure is performed by the memory controller.

Main memory functionality

The data exchange between the processor and RAM takes place using cache memory. The cache memory is managed by a special controller, which studies the running program and analyzes which data may be necessary for the processor in the nearest future. These data are loaded from the main memory to the cache memory in advance and returned, already modified by the processor.

RAM - a device that implements the functions of operating memory. RAM may be located on the same chip as the processor, or be a separate external module.  The RAM contains programs, operating system data, user application programs, and the associated program data.

When you turn on the computer, the necessary drivers, special programs, and operating system elements are written to the RAM. Then, the applications and programs to be run by the user are written to RAM.

To retain the contents of RAM, the operating system saves the contents of RAM to a permanent storage device (hard disk drive or solid-state drive) before shutting down the computer.

The number of tasks the computer can perform at one time varies depending on the amount of RAM available.

Interaction scheme between the RAM and the CPU

1 - Processor;

2 - Cache controller;

3 - Cache memory;

4 - RAM;

5 - Paging file.

In case the RAM cells are insufficient, the swap file gets to work. This file is located on a hard disk or SSD. The swap file keeps a record of information that cannot be stored in the RAM cells. The swap file slows down the system considerably since the swap file is slower than RAM.

What is inside a memory module

1. The board on which the module components are mounted;
2. Memory chips;
3. SPD (Serial Presence Detect) - the chip where the basic settings of the module are stored. When you turn on the system BIOS of the motherboard reads the SPD information and sets the time and frequency of RAM;
4. Key - This is a special slot on the board which identifies the module type. This slot prevents the board from incorrectly installing into the RAM slot;
5. SMD module components (resistors, capacitors). These components provide power control of the chips.

More about DRAM

DRAM memory modules are widely used in computers as operational memory devices.

DRAM is a memory module of a standard design. It consists of:

• A printed circuit board on which the memory chips are located.
• A connector that required to connect the module to the motherboard.

Types of DRAM

• SDR SDRAM (single data rate synchronous DRAM) is a type of DRAM that operates in synchronization with the CPU clock frequency. It has been produced since 1993. The peculiarities of this type of memory are the implementation of a clock generator to synchronize signals and the application of pipeline information processing. Pipeline information processing is the ability to receive (read) a new instruction before the previous instruction is fully resolved (write). This kind of information processing allows more instructions to be executed at the same time. SDR SDRAM has 168 pins and two notches in the connector. Operating frequencies: It operates at 100 MHz or higher on the system bus.
• DDR SDRAM (double data rate SDRAM, or SDRAM II) - synchronous dynamic RAM with double data rate. It has been produced since 2000. It operates similarly to SDR SDRAM, only twice as fast. This type of DRAM can process two read and two write instructions per clock cycle. DDR SDRAM contains 184 pins and one slot in the connector. Operating frequencies are 100, 133, 166, and 200 MHz. The clock frequency ranges from 100 to 200 MHz, and data is transmitted at 2 bits per clock pulse. This means that the effective data transfer frequency is between 200 and 400 MHz.
• DDR2 SDRAM. It has been produced since 2004. It is faster than DDR SDRAM since it can run at higher clock frequencies. It has a large number of pins - 240. Operating frequencies: 200, 266, 333, 337, 400, 533, 575 and 600 MHz. Effective transfer frequencies can be 400, 533, 667, 675, 800, 1066, 1150, and 1200 MHz.
• DDR3 SDRAM is based on DDR2 SDRAM. It has been produced since 2007. It uses the same number of pins as DDR2 SDRAM - 240. It has improved performance due to improved signal processing, higher memory capacity, lower power consumption (1.5 volts), and higher standard clock speed up to 800 to 2400 MHz.
• DDR4 SDRAM - based on previous generations of DDR technology. It has been produced since 2014. There are 288 pins. It is distinguished by higher frequency characteristics and lower supply voltage. DDR4 bandwidth can reach 25.6 Gb/s, in case the effective frequency is increased to 3200 MHz. Secure DDR4 performance is assured by the implementation of a parity mechanism on the instruction address buses. Operating frequencies: A range of 1600 to 2400 MHz was originally set, with the possibility of increasing up to 3200 MHz.
• DDR5 SDRAM - based on the technologies of previous generations of DDR. It has been produced since 2020. The number of pins is 288. It is featured by higher frequency characteristics, maximum module volume, and lower supply voltage. The module bandwidth reaches 32 GB/s, with a maximum effective frequency of 8400 MHz.

DIMM connectors on the motherboard

DIMM is a DRAM memory connector (form factor) that has latches on both ends. These connectors have a different number of pins that are compatible with specific memory module pins.

Central processing unit (CPU)

The processor is responsible for logical and computational operations processing data. It is the main part of the computer. Externally, the CPU is a small square board covered with a metal plate at the top. It is necessary to use a metal cover to protect the microchips. The bottom surface includes a large number of pins. The CPU is installed in a socket on the motherboard.

Any computing device needs a CPU. The CPU is connected to the memory system and the input and output devices.

Components of the processor

The CPU consists of:

• CPU lid. It ensures ingress protection against small particles and prevents mechanical damage. The lid is made of a material with a high thermal conductivity coefficient. Thus, heat can be extracted from the chip, and the CPU temperature is maintained at a normal range.

• The processor crystal.

All computation operations take place through the processor crystal. The crystal is made of silicon. There can be several crystals.

• Textolite plate.

All parts of the processor are attached to this plate. The backside of the textolite plate has a lot of pins.

Integrated graphics processor

Besides the main core, one part of a CPU may be the graphics processor. There is no requirement to have an integrated graphics core, as not every CPU has one. It provides support for graphics.

Integrated graphics are more common in laptops or office desktops, which do not have high graphics requirements.

CPU Throttling

This is a safety mechanism that prevents the CPU from overheating or causing hardware failures during operation. The mechanism activates when the temperature rises to a critical level. As a result, protection is provided by reducing the performance of the core.

Through the BIOS settings, it is possible to forcibly change the trotting settings to overclock the CPU without triggering the protection.

Principle of operation

1. Sequential data processing. The CPU extracts the necessary data from the program code each time a process is started. This data is loaded into the cache memory.
2. Caching means using an additional fast memory to store copies of data blocks from the main (RAM) memory. There is a distinction between level 1, level 2, and level 3 caches. Level 1 cache has the shortest access time and smallest size. Layer 2 cache usually has a much longer access time. Layer 3 cache is the largest and quite slow but still much faster than RAM.
3. Data is divided into two categories when it comes out of the cache: instructions and values. Instructions are redirected to the instruction registers, and values are transferred to the data registers. Registers refer to memory cells (SRAM).
4. Registers provide service to the ALU (arithmetic and logic unit). The ALU supplies power to the processor and processes the mathematical data.

The dotted line indicates the CPU.

• 1. Arithmetic and logic unit (~ 1 KB, 1-2 cycles)
• 2. Registers (~ 100 KB, 2-3 cycles)
• 3. Level 1 instruction cache (~ 100 KB, 2-3 cycles)
• 4. Level 1 data cache (~ 100 KB, 2-3 cycles)
• 5. Level 2 cache (~500 KB, 3-5 cycles)
• 6. Level 3 cache (~ 10-15 MB, 3-5 cycles)
• 7. DRAM - dynamic random-access memory (~ 10 GB, 50-200 cycles)
• 8. Storage space (~ 1000 GB, 50,000 cycles)

5. Computation results are divided into two different parts- finished and unfinished, which are sent back to the cache memory.
6. At the end of the computing cycle, the final result is written to RAM. This is necessary to free up space in the cache buffer, which is needed for new operations.  

Specifications

Clock rate

The rate of cycle transition from one step to the next is determined by the clock. The frequency of the clock pulses per unit time (1 second) is called the clock rate. The measurement unit of the clock frequency is Hertz. The higher the clock rate, the more operations the computer carries out.

When a voltage is applied to the clock resonator, electrical current oscillates due to the action of a quartz crystal. These oscillations are sent to a clock generator, which converts them into pulses that are sent to the data buses.

Bit width

The bit width of the CPU specifies the amount of data processing per clock cycle, which is exchanged between the CPU and the main memory.

The data processing size can be as follows:

• 1 byte (8 bit);
• 2 bytes (16 bits);
• 4 bytes (32 bit);
• 8 bytes (64 bit).

Electric energy consumption

The electric energy consumption of a processor determines its performance. For example, dual-core processors running at low frequencies consume less energy than an octa-core processor.

Architecture

In terms of hardware, the architecture of a CPU (also called microarchitecture) is the internal design of a CPU of the same generation or model.

In terms of software, the architecture of a CPU is the compatibility with a specific set of instructions (x86), their structure (register set, addressing system), and the way they are implemented (program counter). That is the ability of an x86 compatible program to work on the x86 architecture. At the same time, such a program will not work on other systems (e.g., ARM).

Main CPU architectures:

• CISC architecture (Complex Instruction Set Computer).
• RISC architecture (Reduced Instruction Set Computer).
• MISC architecture (Minimal Instruction Set Computer).
• VLIW architecture (Very Long Instruction Word).
• Hybrid architecture.

Motherboard

The motherboard is a multilayer sheet of printed circuit board that contains the copper conductor rails that connect the motherboard's components to one another.

The motherboard and the connected devices are mounted inside the computer case with the power supply and cooling system to form the computer chassis.

Components of a computer motherboard

1. CMOS battery

The battery on the motherboard provides an autonomous power supply for the BIOS after the computer is turned off. Otherwise, the date, time, and BIOS settings will not be saved. In some cases, the computer may not start.

Motherboard has a slot designed to hold one of three types of batteries:

• CR2032 has a capacity of 210-230 mAh;
• CR2025 has a capacity of 150 mAh;
• CR2016 has a capacity of 75-90 mAh.

The voltage of these batteries is 3 V.

The first two letters occurring in the designation define the composition of the battery:

CR is lithium.

The first 2 digits are the diameter in millimeters, the second 2 digits are the thickness in tenths of a millimeter.

A smaller battery can be installed on the laptop's motherboard - for example, CR 1220.

2. The F_USB1 and F_USB2 connectors are used for the USB ports.

Each USB connector on the motherboard supports the connection of two USB ports on the computer chassis.

3. PCI express x16 and PCI express x4.

These are the connectors for connecting video cards.

4. PCI 1, PCI 2 are universal and more obsolete connectors.

Sound cards, network cards, and other expansion cards can be plugged into these slots.

5. TPM connector is a connector to install a TPM cryptoprocessor, which stores cryptographic keys for data protection.

6. PCIE X 1_1 connector, PCIEX 1_2 connector, PCIEX 1_3 connector.

These are modern high-speed connectors with a smaller size. They connect sound cards, TV tuners, network cards, and many different expansion cards.

7. COM connector is a serial port.

This port allows you to connect your computer to an uninterruptible power supply (UPS), satellite receivers, and cash registers. Also, using this port, you can connect two computers into one network.

8. Front panel audio connector

This connector on the motherboard supports the connection of headphones, speakers, or a microphone to the computer chassis.

9. Bus controllers (microcontrollers) are designed to control electronic devices.

10. CPU_ FAN, SYS_FAN1, SYS_FAN2, SYS_FAN3 connectors.

They are used to connect the fans of the cooling system.

11. Connectors for external peripherals such as keyboard, mouse, speakers, etc.

12. ATX_12V connector.

This is an additional eight-pin connector. It is needed for duplicating wires in case of high current consumption by the processor to take the load off the main ATX connector (18).

The 13, 14, 15 elements represent a unified system of power supply unit.

13. MOSFET Transistors.

These transistors make up the VRM voltage regulator module, which controls how much voltage is delivered to components on the motherboard, such as the CPU or graphics card.

14. The chokes create the necessary inductance.

15. The capacitors provide the necessary capacitance.

They absorb the pulses from the power supply to the motherboard socket.

16. CPU socket.

A socket is a slot on the motherboard where the processor is installed. The socket type is the most important specification of the computer. It determines the list of compatible chipsets, processors, motherboards, and cooling systems.

Sockets vary in the number of pins, which usually increases with the power and complexity of the processors.

You should consider the type of socket when choosing a motherboard. Technically, sockets can vary from each other by the availability of additional controllers, performance, and the ability to support the integrated graphics core of the processor.

It is important to remember that if you choose a relatively outdated socket, you cannot upgrade your computer by installing a new processor. When buying a motherboard, it is necessary to study the socket installed in it and the processors supported by this socket.

17. DIMM memory card slots.

18. ATX Connector for power supply unit.

19. Slot M.2. This slot allows you to connect an SSD. MSATS Signature stands for Plug-in SSD Form Factor.

20. Southbridge or chipset. This is located under the heatsink.

It ensures the proper operation of all other devices that are included in the motherboard.

21. The B_BIOS and M_BIOS chips are Dual Bios.

 

M_Bios is the primary microchip. B_Bios is the reserve one if the M_Bios chip fails to update or delete the Bios system.

22 and 23 are SATA 2 (blue) and SATA 3 (white) connectors.

They are dedicated to connect hard drives, CD, DVD drives, and SSD drives. The SATA 2 connector supports speeds up to 3 Gbit/s. The SATA 3 connector is more advanced, as it supports speeds up to 6 Gbit/s.

Chipset

A chipset is a series of chips on the motherboard that ensures the connection between the processor and the peripherals of the system (RAM, storage, USB ports, etc.). The ability to overclock the CPU in many ways depends on the chipset. This chipset is classified as one of the system's most important components. It determines the system's performance, expandability, stability under different settings and conditions, upgrades, etc.

1. Central processor
2. Clock generator
3. Bus
4. Chipset
5. Northbridge. In modern computers, integrated into the CPU.
6. High-speed PCI-Express or AGP bus.
7. Graphics adapter slot
8. Memory bus
9. Memory slots
10. Internal bus
11. Southbridge
12. PCI bus
13. PCI slots
14. Motherboard connectors
15. LPC bus
16. BIOS
17. Super I/O controller.

Form Factor

Form factor is defined as a standard that determines the size of the motherboard for a computer case, which matches one of the three commonly used formats: ATX (1), Micro-ATX (2), Mini-ITX (3).

Dimensions: ATX 305x244 mm; Micro ATX 244x244 mm; Mini ITX 170x170 mm.

Smaller boards allow you to reduce the size of the computer chassis. On these boards, all the elements are mounted close to each other. However, this increases the temperature of the computer case and doesn't allow to make a lot of connectors.

The motherboard form factor that is appropriate for the specific case is listed on the motherboard manufacturer's websites.