1.1 Identify the fundamental principles of using personal computers part 3

> Identify the names, purposes and characteristics of power supplies:

Power Connections on typical modern motherboard

ATX

Today, PCs will use either an ATX or ATX12V power supply. It contains software control of the power on/off signal so that it can shut down the system. Since the ATX/ATX12V power supplies are software activated/deactivated, you need to connect the “Power SW” cable from the chassis to the motherboard. Most power supplies require to have a load connected to the power supply. In other words, you must have at least one component such as a drive or motherboard connected to the power supply.

Most power supplies designed to be used in the United States operate at 120 volts with a frequency of 60 Hz. In other nations, the supply voltage and frequency may be different. In Europe, you will find 230 volt with a 50 Hz frequency as the standard. Today, most PC power supplies will operate at either voltage. Some can automatically switch over to the proper voltage while most are done by using a small switch on the rear of the power supply. Ensure when plugging in your PC and turning it on, the correct voltage is selected. If you have a power supply switched over to 230 V and the voltage is 120 V, the PC will not boot up. Unfortunately, if the power supply is set to 120 V and it is connected to a 230 V outlet, it will seriously damage your power supply and other important components.

The ATX12V power supply provides increased 12 V, 3.3 V, and 5 V current and provides additional cooling capability. An ATX12V power supply can be easily identified by the addition of an additional new 2x2 pin connector and an optional 1X6 pin connector.

ATX Pin Outs

The ATX power supply uses the PS_ON signal to power up the system. A +5 volt signal is constantly sent through pin 14 (PS_ON) of the ATX power connector. When the PS_ON is shorted tells the power supply to turn on and start the boot process. A push button contact switch is connected to two pins on the motherboard that link to the PS_ON signal to ground. When the push button is pushed, it connects the PS_ON signal to ground. When the push button is pushed, it connects the PS_ON signal with ground, shorting it out. Therefore, when you are installing an ATX motherboard, you need to connect the push button wires (usually labeled PWR SW) to the motherboard. If you decide to test a motherboard without physically installing it into an ATX case, you can start the system by either connecting a push button switch to the motherboard and pressing the button or by taking a small screw driver and make contact with the two pins that make up the power switch connector. Since the switch only toggles the on/off status, the switch carries only +5 V of DC power, rather than the full 110 V AC current used in the T power supplies.

Besides supplying the power to the PC components, the power supply also provides the power-good signal. During boot up, the processor tells the computer to constantly reset. As soon as the power supply performs a self-test, testing if all voltage and current levels are acceptable, the power supply will send a power good signal (+5 volts) to the microprocessor. When the power good signal is sent, the computer will finish the boot process.

	ATX Power Supply
	24 pin connection on mainboard, some newer motherboards with 24 pin connections can accept both 20 and 24 pin connectors
	20 and 24 pin main power connectors
	20 main and 4 pin secondary connector - AMD Athlon 64 and Intel Pentium 4 processors require a power supply with an extra 12V connector that is connected to a 4-pin header on the motherboard
	8 Pin cpu connector - On some motherboards, for example boards that support Intel dual-core processors have a secondary 8 pin connection.

The ATX form factor has five main power supply designs:

ATX - 20 pin connector (Used through Pentium III and early Athlon XP)

WTX - 24 pin connector (Pentium II and III, Xeon and Athlon MP)

AMD GES - 24 pin main connector, 8 pin secondary connector (some dual-processor Athlon)

ATX12V - 20 pin main connector, 4 pin secondary connector, 8 pin tertiary connector (Pentium 4 and mid/late Athlon XP & Athlon 64)

EPS12V - 24 pin main connector, 8 pin secondary connector, optional 4 pin tertiary connector (Xeon and Opteron) defined in SSI specification

ATX12V 2.0 - 24 pin main connector, 4 pin secondary connector (Pentium 4, Core 2 Duo, and Athlon 64 with PCI Express)

ATX12V 2.2 - One 20/24-pin connector, one ATX12V 4 pin connector. Many power supply manufacturers include a 4 plus 4 pin, or 8 to 4 pin secondary connector instead, which can also be used as the secondary EPS12V connector.

> Identify the names purposes and characteristics of processor / CPUs

CPU chips:

Central Processing Unit is the component on the motherboard that
interprets instructions and processes data contained in computer programs.

The CPU combines the control unit, storage unit, and arithmetic unit.

• Control unit interprets the instructions given to the computer.
• Internal storage is where the program of instructions is kept and where data from the input devices are sent.
• External storage can consist of disk and tapes.
• Arithmetic unit actually does the calculation required by the program.

CPU technologies:

Hyperthreading is Intel's trademark for their implementation of the
simultaneous multithreading technology on the Pentium 4 microarchitecture. The
technology improves processor performance under certain workloads.

Dual core a CPU that includes two complete execution cores per physical
processor. It has combined two processors and their caches and cache controllers
onto a single integrated chip. Dual-core processors are well-suited for multitasking
environments because there are two complete execution cores instead of one, each
with an independent interface to the frontside bus. Since each core has its own
cache, the operating system has sufficient resources to handle most compute intensive
tasks in parallel.

Throttling is sort of enforced power management: Even when the system
is highly active, the CPU is "put to sleep" for short amounts of time.
This is done when the temperature is critically high, or, by request of the user,
when the system shall use less power to allow longer system usage when on battery
power.

Micro code (MMX) technology is designed to accelerate multimedia and
communications applications by including new instructions and data types that
allow applications to achieve better performance.

Overclocking is the process of forcing a computer component to run at a higher clock rate than it was designed for or was designated by the manufacturer.

Cache memory is used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are to cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.

Voltage Regulator Module (VRM) is an electronic device that provides a microprocessor the appropriate supply voltage. It can be soldered to the motherboard or be an installable device. It allows processors with different supply voltage to be mounted on the same motherboard.

Some voltage regulators provide a fixed supply voltage to the processor, but most of them sense the required supply voltage from the processor. In particular, VRMs that are soldered to the motherboard are supposed to do the sensing, according to the Intel specification.

Speed (real vs. actual) Between 2001 and 2003, Intel and AMD made few changes to the designs of their processors. Most performance increases were created by raising the processor's clock speed rather than improving the microprocessor's core. Around mid 2004, Intel encountered serious problems in increasing their Pentium 4's clock speed beyond 3.4 GHz because of the enormous amount of heat generated by the already hot Prescott core processor when working at higher clock speeds. In response, Intel started exploring ways to improve the performance of its microprocessors in ways other than raising the clock speeds of the processors such as increasing the sizes of the processors' caches and using multiple processing cores in its processors.

Because of the philosophy change, a Pentium 4 clocked at 3.0 GHz with a 1MB L2 cache could now outperform a 3.4 GHz Pentium 4 with 512KB L2 Cache. Clock speeds could no longer solely differentiate the performance of different Pentium 4s. As a result, Intel has adopted a PR rating of its own using three digit numbers. Intel now faces the challenge of making consumers compare its processors based on PR ratings rather than raw clock speed, ironically a problem which Intel created itself.

Some analysts regard the PR scheme (and a raw MHz/ GHz rating) as nothing more than a marketing tactic, rather than as a useful measure of CPU performance. Many professionals or interested amateurs now consult extensive benchmark tests to determine system performance on various applications.

32 vs. 64 bit A change from a 32-bit to a 64-bit architecture is a fundamental alteration, as most operating systems must be extensively modified to take advantage of the new architecture. Other software must also be ported to use the new capabilities; older software is usually supported through either a hardware compatibility mode (in which the new processors support the older 32-bit version of the instruction set as well as the 64-bit version), through software emulation, or by the actual implementation of a 32-bit processor core within the 64-bit processor die (as with the Itanium processors from Intel, which include an x86 processor core to run 32-bit x86 applications). The operating systems for those 64-bit architectures generally support both 32-bit and 64-bit applications.

> Identify the names, purposes and characteristics of memory

Types of memory:

Common DRAM PIN Count:

• DIMM 168-pin (SDRAM)
• DIMM 184-pin (DDR SDRAM)
• DIMM 240-pin (DDR2 SDRAM)

DRAM: Dynamic Random Access Memory, stores data as electronic signals. These signals must be constantly refreshed to keep them from dissipating.

SRAM: Synchronous Random Access Memory.

SDRAM: Synchronous Dynamic Random-Access Memory. A DRAM technology that uses a clock to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are "in synch." The synchronization eliminates time delays and allows for fast consecutive read and write capability, thereby increasing the overall performance of the computer. SDRAM has two separate memory banks that operate simultaneously, while one bank prepares for access, the other is being accessed. SDRAM is controlled by the system clock. SDRAM can only be used in computers designed for it and cannot be mixed with any other type of memory. SDRAM can operate at 100MHz, 133Mhz and features a burst mode that allows it to address blocks of information instead of small data bits.

DDR / DDR2

DDR (DOUBLE DATA RATE) finds its foundations on the same design core of SDRAM, yet adds advances to enhance its speed capabilities. As a result, DDR allows data to be sent on both the rising and falling edges of clock cycles in a data burst, delivering twice the bandwidth of standard SDRAMS. DDR essentially doubles the memory speed from SDRAMs without increasing the clock frequency.

DDR memory modules have 184 pins and one notch
near the center, while DDR2 have 240 pins.

The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, allowing transfers from two different cells to occur in the same memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

DDR2 DIMMs are not backwards compatible with DDR DIMMs. The notch on DDR2 DIMMs is in a different position than DDR DIMMs, and the pin density is slightly higher than DDR DIMMs. DDR2 is a 240-pin module, DDR is a 184-pin module.

• 184-pin DIMM: DDR 200/266/333/400 DDR SDRAM
• 240-pin DIMM: DDR2 400/533/667/800 DDR-2 SDRAM

DOUBLE DATA RATE 3 SYNCHRONOUS DRAM (DDR3 SDRAM)

DDR3 is the third generation of Double Data Rate (DDR) SDRAM memory. Similar to DDR2, it is a continuing evolution of DDR memory technology that delivers higher speeds (up to 1600 MHz), lower power consumption and heat dissipation. It is an ideal memory solution for bandwidth hungry systems equipped with dual and quad core processors and the lower power consumption is a perfect match for both server and mobile platforms. DDR3 modules will be available in the second half of 2007.

RAMBUS: Direct Rambus DRAM or DRDRAM (sometimes just called Rambus DRAM or RDRAM) is a type of synchronous dynamic RAM, designed by the Rambus Corporation. Not widely in PC's today.

Operational characteristics:

Parity versus non-parity

Parity is a quality control method that checks the integrity of data stored in a computer's memory. Parity works by adding an extra bit of data to each byte to make the total number of 1's either odd or even. An error is detected if the parity circuit determines that this number has changed, indicating that some of the data may have been lost or otherwise corrupted. Two different parity protocols exist, even parity and odd parity. Parity protocols are capable of detecting single bit errors only. To enable multiple-bit error detection, manufacturers must use a more advanced form of error checking called Error Correcting Code (ECC).

ECC vs. non-ECC

Error Correction Code. A method used to check the integrity of data stored in memory . ECC memory improves data integrity by detecting errors in memory and is more advanced than parity because it can detect both multiple-bit errors and single-bit errors (parity only detects single-bit errors). ECC is typically found in high-end PCs and file servers where data integrity is key.

• Most computers designed for use as high-end servers support ECC memory.
• Most computers designed for use at home or for small businesses do not use ECC memory.

Single-sided vs. double-sided

A physical terms meaning that the memory chips are arranged on one or both sides of the memory module.