Dual-Channel and Triple-Channel Memory
x86 (32-bit) and x86-64 (64-bit) processors have a 64-bit data bus, the same size data bus as on DIMMs. Therefore, memory can be added one module at a time.
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However, to improve performance, many recent systems support dual-channel or triple-channel memory. In these systems, you can add two or three matched memory modules (modules with the same speed and timing characteristics, and for most motherboards, they should also be the same size in GB), and the system will access them as a single very wide module for increased speed. To determine if a particular system or motherboard supports these memory access methods, check the documentation. If you don’t use matched modules or if the modules are not installed in the correct sockets, the memory will be accessed as separate 64-bit modules, providing lower memory perfor-mance than with dual-channel or triple-channel access.
Other Types of RAM
The RAMBUS Inline Memory Module (RIMM) uses a proprietary 184- or 232-pin slot. This RAM, often called RDRAM, is found in some game console systems and a limited number of PCs. On such systems, empty RIMM slots must be filled with Continuity RIMM (CRIMM) modules.
Laptops use a small form factor called Small Outline DIMM (SODIMM). Many netbooks, Ultra Mobile PCs (UMPC), and portable devices, such as cell phones and PDAs, use a MicroDIMM form factor. Figure 1-5 compares the relative size and form factors found in RAM.
| SDRAM 168-Pin 5.375 inch by 1 inch | RDRAM 232-Pin RIMM 5.25 inch by 1.37 inch |
| DDR 184-Pin 5.375 inch by 1 inch | RDRAM 184-Pin RIMM 5.25 inch by 1.25 inch |
| DDR2 240-Pin 5.25 inch by 1.18 inch | SODIMM 144-Pin 2.625 inch by 1 inch |
| DDR3 240-Pin 5.25 inch by 1.18 inch | SODIMM DDR2 200-Pin 2.625 inch by 1.18 inch |
| MICRODIMM 144-Pin 1.545 inch by 1 inch |
Figure 1-5 Memory module comparison.
Chapter 1: Hardware 11
VRAM and Virtual RAM
VRAM is video RAM for the use of the graphic processing unit (GPU). Most GPUs now use vari-ations on SDRAM. VRAM does not stand for virtual RAM. Virtual RAM (more often referred to as a virtual memory, paging file, or swap file) is space on the hard disk drive (HDD) that the RAM uses as an overflow area.
Parity and ECC
Parity is a method of verifying data integrity. It is used when the reliability of the data is more important than the speed at which it is written or read. Parity adds a bit to each byte so that every byte is an even number. When the data is read or received, the bytes should still be even. If not, the data is corrupt. Parity is used in some network communications, hard drives, and RAM, primarily in servers and workstations. Error correction code (ECC) detects and fixes corrupt data in RAM. Both parity and ECC decrease memory performance, but increase reliability.
BIOS
The options selected for the BIOS are stored on the complementary metal-oxide semiconductor (CMOS) chip that is on the motherboard. The BIOS handles fundamental system configuration. The CMOS chip is actually a combination of NVRAM (nonvolatile RAM, which can retain its contents without power) and volatile RAM. The BIOS chip also contains NVRAM, which allows the BIOS to be updated (flashed). If the BIOS cannot recognize a new device, updating the BIOS is a solution. A small battery maintains a charge so that the settings are not lost in the RAM when the PC is off. If the date and time reset when the computer restarts, replace the battery. The BIOS allows you to do the following:
Enable/disable integrated devices Order the boot sequence
Manage drive controllers
View PC diagnostic information such as CPU and motherboard temperatures and onboard fan speeds
Configure CPU and memory speeds and timing Adjust power management settings
The BIOS feature that provides for these settings to be changed is often referred to as the CMOS setup program, because the CMOS stores the values that you select. Figure 1-6 illustrates a typical CMOS setup program’s main menu.
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Figure 1-6 This Award CMOS setup program offers a wide range of adjustments in its menus.
Table 1-4 provides a detailed discussion of the most important CMOS/BIOS settings. Use this table as a quick reference to the settings you need to make or verify in any system. Examples of these and other settings are provided in the following sections.
Table 1-4 Major CMOS/BIOS Settings
Option Settings Notes
Boot Sequence Hard disk, optical (CD/
DVD, Blu-ray), USB,
floppy, network ROM;
order as desired
To boot from bootable Windows or diagnostic CDs or DVDs, place CD or DVD (optical) drive before hard drive in boot sequence; to boot from bootable USB device, place the USB device before the hard drive in the boot sequence. You can enable or disable addi-tional boot devices on some sys-tems.
Memory Configuration By SPD or Auto
(default); Manual set-
tings (Frequency, CAS
Latency [CL], Fast R-2-R
turnaround, and so on)
also available
Provides stable operation using the settings stored in memory by the vendor; use manual settings for overclocking (running memory at faster-than-normal speeds or to enable memory of different speeds to be used safely by selecting slower settings).
| Chapter 1: Hardware 13 | ||
| Option | Settings | Notes |
| CPU Clock and | Automatically detected | Faster or higher settings overclock |
| Frequency | on most recent systems | the system but could cause insta- |
| bility; some systems default to low | ||
| values if the system doesn’t start | ||
| properly. |
Hardware Monitor Enable display for all
fans plugged into the
motherboard
Also known as PC Health on some systems; can be monitored from within Windows with vendor-supplied or third-party utilities.
| Onboard Audio, Modem, | Enable or disable | Enable if you don’t use add-on |
| or Network | cards for any of these functions; | |
| disable each setting before install- | ||
| ing a replacement card. Some | ||
| systems include two network | ||
| adapters. | ||
| PS/2 Mouse | Varies with mouse type | Disable if you use USB mouse; |
| some systems use a motherboard | ||
| jumper. | ||
| USB Legacy | Enable if USB keyboard | Enables USB keyboard to work |
| is used | outside of Windows. | |
| Serial Ports | Disable unused ports; use | Avoid setting two serial ports to |
| default settings for port | use the same IRQ. | |
| you use |
Parallel Port Disable unused port; use
EPP/ECP mode with
default IRQ/DMA if
parallel port or device is
connected
Compatible with almost any paral-lel printer or device; be sure to use an IEEE-1284-compatible printer cable.
| USB Function | Enable | If motherboard supports USB 2.0 |
| (Hi-Speed USB) ports, be sure to | ||
| enable USB 2.0 function and load | ||
| USB 2.0 drivers in Windows. | ||
| USB 3.0 Function | Enable | USB 3.0 ports also support USB |
| 2.0 and USB 1.1 devices. Disable | ||
| if USB 3.0 drivers are not avail- | ||
| able for operating system. | ||
| Keyboard | Numlock, auto-repeat | Leave at defaults (NumLock On) |
| rate/delay | unless keyboard has problems. | |
| Plug-and-Play OS | Enable for all except | When enabled, Windows config- |
| some Linux distributions, | ures devices. | |
| Windows NT, MS-DOS |
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Table 1-4 Continued
| Option | Settings | Notes |
| Primary VGA BIOS | Varies | Select the primary graphics card |
| type (PCIe or AGP) unless you | ||
| have PCIe or AGP and PCI graph- | ||
| ics (video) cards installed that | ||
| won’t work unless PCI is set as | ||
| primary. | ||
| Shadowing | Varies | Enable shadowing for video BIOS; |
| leave other shadowing disabled. | ||
| Quiet Boot | Varies | Disable to display system configu- |
| ration information at startup. | ||
| Boot-Time Diagnostic | Varies | Enable to display system configu- |
| Screen | ration information at startup. | |
| Virtualization | Varies | Enable to run hardware-based |
| virtualization programs such as | ||
| Windows Virtual PC so you can | ||
| run multiple operating systems, | ||
| each in its own window. | ||
| Power Management | Enable unless you have | Enable CPU fan settings to receive |
| (Menu) | problems with devices | warnings of CPU fan failure. |
| S1 or S3 standby | Enable S3 | Use S1 (which saves minimal |
| power) only if you use devices that | ||
| do not properly wake up from S3 | ||
| standby. | ||
| AC Pwr Loss Restart | Enable restart or Full on | Prevents system from staying |
| down if power failure takes place. |
Wake on LAN (WOL) Enable if you use WOL-
compatible network card
or modem
WOL-compatible cards use a small cable between the card and; some integrated network ports also sup-port WOL.
| User / Power-On | Blocks system from | Enable if physical security settings |
| Password | starting if password not | are needed, but be sure to record |
| known | password in a secure place. | |
| Setup Password | Blocks access to setup if | Both passwords can be cleared on |
| password not known | both systems if CMOS RAM is | |
| cleared. | ||
| Chapter 1: Hardware 15 | ||
| Option | Settings | Notes |
| Write-Protect Boot | Varies | Enable for normal use, but disable |
| Sector | when installing drives or using a | |
| multiboot system; helps prevent | ||
| accidental formatting, but might | ||
| not stop third-party disk-prep soft- | ||
| ware from working. | ||
| Boot Virus Detection | Enable | Stops true infections but allows |
| (Antivirus Boot Sector) | multiboot configuration. | |
| Floppy Drive | Usually 3.5-inch 1.44MB | Set to actual drive type/capacity; |
| some systems default to other | ||
| sizes; disable if no drive is present. | ||
| PATA (IDE), SATA | Varies | Autodetects drive type and settings |
| Drives | at startup time; select CD/DVD | |
| for CD/DVD/Blu-ray drive; select | ||
| None if drive not present or to dis- | ||
| able an installed drive. | ||
| SATA Drive | IDE, AHCI, RAID | IDE setting emulates PATA drives. |
| configuration | To take advantage of hot swap- | |
| ping and native command queuing | ||
| (NCQ) to improve performance, | ||
| select AHCI. Select RAID if the | ||
| drive will be used as part of a | ||
| RAID array. | ||
Motherboards
A motherboard connects everything inside your PC. It connects the CPU with memory, integrated I/O ports, storage devices, video, and adapter cards:
Chipsets built in to the motherboard help direct and process data and commands for the CPU.
A processor socket allows the CPU to connect to the computer.
Memory sockets enable a variety of memory sizes and speeds to be installed as needed.
Integrated ports provide access to printers, multifunction devices, external storage, and other components.
The motherboard provides power to the CPU by adjusting the power received from the power supply to the appropriate voltage levels needed for a particular CPU.
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Thermal components on the motherboard measure the temperature and controls fans to cool the CPU.
The motherboard shuts down the PC if the CPU is too hot to prevent damage.
Figure 1-7 shows a typical ATX motherboard and its major components.
1. CPU
2. ATX 24-pin power supply connector
3. Memory sockets
4. PATA interface
5. SATA interfaces
6. USB port headers
7. Floppy drive interface
8. LPT port header
9. COM port header
10. 1394 port header
11. PCI 32-bit slots
12. PCIe x1 slots
13. PCIe x16 slot
14. Port cluster
15. ATX12V power connector
Figure 1-7 An ATX motherboard with PCIe x16 and PCIe x1 expansion slots.
Form Factors
There are a few basic form factors for motherboards. ATX is the basis of all modern motherboards, including Micro-ATX and ITX (refer to Figure 1-7 for a typical ATX motherboard). BTX reverses the positions of components versus ATX and is designed for superior cooling of components such as memory and the CPU (processor). Although some vendors use the BTX form factor for com-puters sold at retail, ATX dominates the field of custom-built computers and aftermarket chassis. There are countless motherboard sizes and capabilities. Table 1-5 outlines the common form fac-tors.