Motherboards
The motherboard, or system board, contains the central processing unit (CPU), BIOS, other processing chips, memory, IO device connections, expansion slots, and more. Over the years, the motherboard has increasingly taken more functions from what was historically installed as expansion cards. For example, many computers you buy today have all of your typical input connectors (keyboard, mouse, USB), and added in Firewire (IEEE1394), video, network, audio (input and output), IDE, SCSI, SATA, and more.
The primary purpose of the motherboard is to process instructions from the operating system and applications. The processing is performed by the CPU which we will discuss in the next section. The motherboard stores active information in the memory and facilitates sending data to the hard drives through the drive interface.
Motherboards are not typically considered a field replaceable unit by consumers, but is replaceable by a certified vendor technician. A field replaceable unit is a component which is able to replaced in the field – not requiring the computer be sent in to be repaired. For example, a hard drive is replaceable while a CPU is not.
There are many different motherboard vendors and thousands of different types of motherboards. A motherboard is unique to a certain chipset and family of processor. For example, a vendor might create one motherboard which is compatible with the Intel Socket 370 series of chips and a different motherboard which is compatible with AMD’s AM2 Sempron series of chips.
Processors (CPUs)
Processors, or Central Processing Units (CPUs), are the chips that are at the core of the computer system and process instructions and direct information between all of the other chips, memory, and storage systems on the computer.
For the A+ Essentials 2006 exam, you will need to know common 32-bit and 64-bit processors and how they work. There are two main CPU manufacturers: Intel and AMD. Each has a full line of 32-bit and 64-bit processors. There are other CPU manufacturers such as IBM, Motorola, and VIA, but each of these is small market share or specialized for a specific purpose (e.g. IBM/Motorola PowerPC in the old PPC line of Macintosh computers). VIA (Cyrix) makes Intel-compatible chips, but is a small player compared to Intel and AMD.
32-bit Processors
Most computers built in the last decade, and a majority of those being built today, use a 32-bit processor. The Intel compatible 32-bit chips are often referred to as “32-bit x86 architectures.” Intel licensed early 32-bit chips to other manufacturers but declined to license the Pentium models, so AMD and Cyrix began designing their own 32-bit chips.
64-bit Processors
AMD introduced the first 32-bit backwards compatible architecture, the AMD64, in September 2003. Intel subsequently released their version of x86-64 chips and 64-bit chips were brought to the Windows desktop. The AMD and Intel chips can run 32-bit software, but Microsoft, Apple, and Linux has Operating Systems written to run in native 64-bit code. Microsoft calls their OSes Windows XP 64-bit edition and Windows Vista x64. One of the big differences between the 64-bit edition and 32-bit edition is the use of device drivers. The 64-bit editions of the Windows OS required native 64-bit signed device drivers to recognize and properly use hardware. If you are running a system with hardware with no 64-bit drivers, you may run into problems.
Multi-Core Processors
If you wanted to increase the speed of a computer, you could install multiple processors. Running multiple processors is an expensive proposition and required you to have a motherboard designed for it. Additionally, if you have a one processor machine and add a second processor, you will need to reinstall the Operating System for the system to function properly. Please Note: you are almost guaranteed to see a question about this: I have on multiple CompTIA certification exams. If you want to upgrade your computer to dual processors, you must reinstall Windows as the HAL is based on the number of processors you have in your machine.
Microprocessor manufacturers wanted to get more performance out of their chips so they began designing chips with multiple microprocessors in one chip. By 2007, it is very common to see desktops, laptops and servers with a dual-core processor – one which has two microprocessing cores in it. Quad-core, or chips with four processors, are becoming increasingly common in datacenters and specialized workstations.
Some high end manufacturers, such as Sun Microsystems, build systems with 8-core CPUs.
RISC versus CISC
You should be familiar with the two general terms for processors: RISC and CISC. Originally, most processors began as CISC chips – Complex Instruction Set Computer – while high end systems had RISC chips – Reduced Instruction Set Computer. RISC chips were designed to required a fewer number of instructions to do tasks which resulted in faster speeds.
Over time, CISC has been able to catch up in terms of speed to RISC chips. The PowerPC is an example of a desktop RISC chip – used in older Apple Macintoshes. Apple has since moved their platform to a 64-bit Intel core.
Memory
Memory is referring to RAM, or Random Access Memory. RAM is a volatile type of computer data storage. RAM are integrated circuits which can be accessed “randomly” – the data stored on the chips is accessed in any order.
RAM is volatile – it loses the data stored on it when the computer is turned off – versus hard drive storage which is non-volatile, turn off the computer and the data isn’t lost.
RAM is used for storing the working area of the OS, applications, and data. RAM comes in memory “sticks” which insert into slots on the motherboard. RAM can be removed and upgraded very easily – and depending on the type of memory, could be upgraded a chip at a time. Other upgrade configurations include upgrading two chips at a time or four chips at a time.
As an IT technician, you will need to learn the differences between types of RAM and the technologies they use to ensure you properly upgrade or switch out memory in PCs.
A RAM module is the gum-pack size chip which plugs into the motherboard. On the RAM module, there are several memory chips.
DIMM Chips
A DIMM, or Dual Inline Memory Chip, is a major type of memory which is replacing SIMM, or single in-line memory modules. SIMMs have a 32-bit data path while DIMMs have a 64-bit data path. Most new chips have at least a 64-bit bus width, so it would require two “matched” SIMMs, versus a single 64-bit DIMM.
The most common types of DIMMs are:
- 72-pin DIMM, used for FPM DRAM and EDO DRAM
- 72-pin SO-DIMM, used for FPM DRAM and EDO DRAM
- 100-pin DIMM, used for printer SDRAM
- 144-pin SO-DIMM, used for SDR SDRAM
- 168-pin DIMM, used for SDR SDRAM (less frequently for FPM/EDO DRAM in workstations/servers)
- 184-pin DIMM, used for DDR SDRAM
- 200-pin SO-DIMM, used for DDR SDRAM and DDR2 SDRAM
- 240-pin DIMM, used for DDR2 SDRAM and FB-DIMM DRAM
For various technologies, there are certain bus and device clock frequencies that are standardized. There is also a decided nomenclature for each of these speeds for each type.
SDRAM DIMMs - These first synchronous registered DRAM DIMMs had the same bus frequency for data, address and control lines.
- PC66 = 66 MHz
- PC100 = 100 MHz
- PC133 = 133 MHz
DDR SDRAM (DDR1) DIMMs - DIMMs based on Double Data Rate (DDR) DRAM have data but not the strobe at double the rate of the clock. This is achieved by clocking on both the rising and falling edge of the data strobes.
- PC1600 = 200 MHz data & strobe / 100 MHz clock for address and control
- PC2100 = 266 MHz data & strobe / 133 MHz clock for address and control
- PC2700 = 333 MHz data & strobe / 166 MHz clock for address and control
- PC3200 = 400 MHz data & strobe / 200 MHz clock for address and control
DDR2 SDRAM DIMMs - DIMMs based on Double Data Rate 2 (DDR2) DRAM also have data and data strobe frequencies at double the rate of the clock. This is achieved by clocking on both the rising and falling edge of the data strobes. The power consumption of DDR2 is significantly lower than DDR(1) at the same speed.
- PC2-3200 = 400 MHz data & strobe / 200 MHz clock for address and control
- PC2-4200 = 533 MHz data & strobe / 266 MHz clock for address and control
- PC2-5300 = 667 MHz data & strobe / 333 MHz clock for address and control
- PC2-6400 = 800 MHz data & strobe / 400 MHz clock for address and control
Chip speed data from: http://en.wikipedia.org/wiki/DIMM
Review this resource to understand how to install different types of memory: http://www.oempcworld.com/support/How_to_Install_PC_Memory.htm
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