1.1 Identify the fundamental principles of using personal computers part 2

> Memory slots

RIMM Slots: were commonly used on the Intel Pentium 4 motherboards. Unlike most other types of computer memory, computers that support RIMM require a continuous signal. If a memory slot is left empty the PC will not work. The empty slot must be filled with another RIMM module or a C-RIMM pass through module which enables a continuous signal.

< Installed DIMM < Open DIMM Slots   DIMM Slots: come in three common pin configurations. 240-pin slots - for DDR2 SDRAM memory for desktop computers. 184-pin slots - for DDR SDRAM memory for desktop computers. 168-pin slots - commonly found in Pentium and Athlon systems.

Processor sockets

A motherboard is designed for a certain range of processors. One of the determining factors of processor compatibility is the slot or socket connector soldered onto the board. 242-contact and 330-contact slot connectors were used for a short time to allow for L2 cache to be packaged close to the processor die. Processor manufacturing advancements now allow L2 cache to be manufactured on the same die as the processor, requiring a smaller form-factor processor packaging. PGA (pin grid array) sockets are more common, flexible, and compact, but have many variations in the amount of pin connects and pin layouts.

AMD Proccessors

INTEL Proccessors

External cache memory

L2 Cache: Now usually found on the processor. The size of 2nd level cache. L2 Cache is ultra-fast memory that buffers information being transferred between the processor and the slower RAM in an attempt to speed these types of transfers.

L3 Cache: Is a type of cache that is found on the motherboard instead of the processor. The size of 3rd level cache, typically larger then L2. L3 Cache is ultra-fast memory that buffers information being transferred between the processor and the slower RAM in an attempt to speed these types of transfers. Integrated Level 3 cache provides a faster path to large data sets stored in cache on the processor. This results in reduced average memory latency and increased throughput for larger High-end Desktop workloads.

Bus architecture

Front side buses serve as a backbone between the CPU and a chipset. The chipset (northbridge and a southbridge) is the connection point for all other buses in the system. The PCI, AGP, and memory buses all connect to the chipset to allow for data to flow between the connected devices.

Chipsets

The motherboard chipset consists of a north bridge, or Memory Controller Hub (MCH), which is responsible for controlling communication between system memory, the processor, AGP, and the south bridge, or I/O Controller Hub (ICH). The ICH controls communication between PCI devices, system management bus, ATA devices, AC'97 (audio), USB, IEEE1397 (firewire), and LPC controller. These chipsets are soldered onto the motherboard and cannot be changed or upgraded.

Bus slots

	PCI: Peripheral Component Interconnect, is a specification introduced by Intel Corporation that defines a local bus system that allows up to 10 PCI-compliant expansion cards to be installed in the computer. Many netword, modem, sound, and graphics adapters et... use the PCI bus. The PCI bus is being replaced by PCI Express AGP: Accelerated Graphics Port , used for graphics adapters. The AGP port is being replaced by the new PCIe slot. PCIe: PCI Express (PCIe) is a new I/O bus technology that, over time, will replace Peripheral Component Interconnect (PCI), PCI-X, and the Accelerated Graphics Port (AGP). PCIe hardware is backwards compatible with PCI software (not with hardware PCI slots) on the Microsoft Windows 2000 and Microsoft Windows XP operating systems. The PCI features supported by current Windows operating systems will continue to work with PCIe without any need for modifications in the applications, drivers, or operating system; however, the advanced PCIe features will be natively supported only in Windows Vista and later versions of Windows. PCIe slots today are mostly used for graphics cards which require the greater bandwidth PCIe is capable of. AMR: Audio Modem Riser, is an expansion slot found on the motherboards of some Pentium III, Pentium 4, and Athlon personal computers. Drawbacks of AMR are that it eliminates one PCI slot, it is not plug and play, and it does not allow for hardware accelerated cards (only software-based). CNR: Communications and Networking Riser, is a slot found on some motherboards. A motherboard manufacturer can choose to provide audio, networking, or modem functionality in any combination on a CNR card. Today nearly all riser technologies, such as ACR, AMR, and CNR, have been generally obsoleted in favor of on-board or embedded components.
	PATA: In 2003, the original ATA (Advanced Technology Attachment) was retroactively renamed Parallel ATA (PATA) IDE: Integrated Drive Electronics EIDE: Enhanced IDE, sometimes referred to as Fast ATA or Fast IDE Are standard interfaces for connecting storage devices such as hard disks and CD-ROM drives inside personal computers.
	SATA: Serial ATA (Advanced Technology Attachment) is a computer bus technology primarily designed for transfer of data to and from hard disks and optical drives. The SATA connectors will only fit in one orientation. The main differences between the serial interconnect and the parallel interconnect of ATA are as follows: Serial ATA is point to point, meaning only one storage device can be connected to a single Serial ATA cable. Parallel ATA has a shared channel and can connect up to two storage devices on a single cable. Serial ATA is faster. Currently Serial ATA transfers data at a rate of 150 megabytes (MB) per second and will likely advance to 300 MB and 600 MB per second in the near future. Serial ATA has a thinner cable and a smaller connection that is keyed so they cannot be connected incorrectly, unlike some parallel ATA cables.

SCSI Technology

Small Computer System Interface) is a set of standards for physically connecting and transferring data between computers and peripheral devices. SCSI interfaces that have an 8-bit data bus, referred to as narrow, allow up to seven devices (hard drives, tape drives, CD-ROM drives, removable drives/disks and scanners) connected to one SCSI adapter/controller. It would be eight devices if you count the controller card. SCSI interfaces with 16-bit data bus, referred to as wide, interfaces allow up to 15 devices (16 devices including the controller card).

Types of SCSI interfaces:

• SCSI-1: Uses an 8-bit bus, supports data transfer speeds of 4 MBps.
• SCSI-2: Uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices. It is currently the most common type of SCSI. Data transfer speeds are typically around 5 MBps.
• Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit data transfers.
• Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data transfer speeds of 10 MBps.
• Fast Wide SCSI: Uses a 16-bit bus and supports data transfer speeds of 20 MBps.
• Ultra SCSI: Uses an 8-bit bus, supports data rates of 20 MBps.
• SCSI-3: Uses a 16-bit bus, supports data rates of 40 MBps. Also called Ultra Wide SCSI.
• Ultra2 SCSI: Uses an 8-bit bus, supports data transfer speeds of 40 MBps.
• Wide Ultra2 SCSI: Uses a 16-bit bus, supports data transfer speeds of 80 MBps.

SCSI Termination

The two SCSI devices at either end of the chain must be terminated; the other devices should not be terminated. If only an internal cable is used, the adapter card and the device at the end of the cable need to be terminated, but the other devices in between should not be terminated. If using an internal cable and an external cable, the two devices located at the end of each cable should be terminated. To terminate or not terminate a device, the terminators are inserted/removed or enabled/disabled with jumpers or DIP switches. Some SCSI devices can be automatically terminated.

To terminate/not terminate a device, you would either insert or remove the terminators on the end device or enabled/disabled them with jumpers or DIP switches. Some SCSI devices have automatic termination. Today, most have a jumper to enable or disable the termination.

Internal daisy chain
(image from intel.com)

External daisy chain (image from intel.com)

Internal External daisy chain (image from intel.com)

There are several different kinds of termination used on SCSI buses. They differ in the electrical circuitry that is used to terminate the bus. Better forms of termination make for more reliable SCSI chains; the better the termination, the fewer problems (all else being equal) with the bus, though cost is generally higher as well. In general terms, slower buses are less particular about the kind of termination used, while faster ones have more demanding requirements. In addition, buses using differential signaling (either HVD or LVD) require special termination.

• Passive terminator – The passive terminator uses special electrical resistors to act as voltage dividers. Since they help ensure that the chain has the correct impedance load, they prevent signals from reflecting or echoing when the signal reaches the end of the chain. Passive terminating resistors work well for chains of short distances (2-3 feet) and slower speeds (SCSI-1 specification). The chain should never exceed 6 meters. It is for single-ended SCSI buses only that should only be used in narrow (8-bit) SCSI busses running at 5 MHz.
• Active Termination – Active termination acts as voltage regulator to maintain a stable voltage through the chain by utilizing the termination power lines to compensate for voltage drops. Since the active termination helps reduce noise, it allows for longer cable lengths and faster speeds. In fact, active termination is the minimum required for any of the faster-speed single-ended SCSI buses. The chain should never exceed 18 meters. It is for single-ended SCSI buses only.
• Forced Perfect Terminator (FPT) – The Forced Perfect Terminator diode clamps are added to the circuitry to automatically match the line impedance by forcing the termination to the correct voltage thus allowing “perfect” termination. It is for single-ended SCSI buses only and should be used for single-ended applications that experience high levels of electrical noise.
• High Voltage Differential (HVD) – Buses using high voltage differential signaling require the use of special HVD terminators.
• Low Voltage Differential (LVD) – Newer buses using low voltage differential signaling also require their own special type of terminators. In addition, there are special LVD/SE terminators designed for use with multimode LVD devices that can function in either LVD or SE modes; when the bus is running single-ended these behave like active terminators. Note: Many internal cables have a built-in LVD terminator at the end of the cable.

> BIOS / CMOS / Firmware

Basic input/output system (BIOS) is the set of essential software routines that test hardware at startup, start the operating system, and support the transfer of data among hardware devices. The BIOS is stored in read-only memory (ROM) so that it can be executed when you turn on the computer. Although critical to performance, the BIOS is usually invisible to computer users.

The BIOS Setup Utility displays the PC system’s configuration status and provides you with options to set system parameters. The parameters are stored in battery-backed-up CMOS RAM that saves this information when the power is turned off. When the system is turned back on, the system is configured with the values you stored in CMOS.

Most BIOS Setup Utilities enable you to configure:

• Hard drives, diskette drives and peripherals
• Video display type and display options
• Password protection from unauthorized use
• Power Management feature

(CMOS) complementary metal oxide semiconductor is an on-board semiconductor chip powered by a CMOS battery inside IBM compatible computers that stores information such as the system time and system settings for your computer.

Firmware is software that is embedded in a hardware device. It is often provided on flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user. Most devices attached to modern systems are special-purpose computers in their own right, running their own software. Some of these devices store that software ("firmware") in a ROM within the device itself. Over the years, however, manufacturers have found that loading the firmware from the host system is both cheaper and more flexible. As a result, much current hardware is unable to function in any useful way until the host computer has fed it the requisite firmware. This firmware load is handled by the device driver.

Riser card / daughter board

Riser card is a PC expansion card that can be added to a PC to give it audio, modem or networking capabilities.

Daughter boards are expansion boards that commonly connect directly to the motherboard and give the computer an added feature such as modem, audio capability ect.. . Today, these types of boards are not found or used in desktop computers and have been replaced with PCI boards. But, many laptops still use these types of boards.