2We Need to Talk!The CPU needs some method to talk to the devices to tell them what to doThe devices need some way to send data to, and receive data from the CPUWe need to expand our logical model from the CPU chapter
4RAMNorthbridgeCPUAddress BusEDBSouthbridgekeyboardVideo CardHard Disk Drive
5ChipsetAddress BusNorthbridgeRAMCPUEDBChipsetSouthbridgeKeyboardControllerVideo CardHard Disk Drive
6Problems Different motherboards have different keyboard controllers We need specific code to talk to the controllerWe need a place to store this specific programming and the programming for other devices (optical drive, floppy, etc.)
7SolutionUse a ROM chipDoes not “forget” when power is removed, like RAM doesSpecific to motherboard and devices on itRead only, code does not changeCan hold lots of programs, like a “chapter book”This is called “firmware”
9System ROM Holds all the support programming for basic devices Is given a specific address space, or range of memory addresses for its code
10Basic Hardware CPU Mouse Keyboard Video card RAM Network card Sound CardFloppy driveHard Disk driveZip driveUSB portsCD-ROM drive
11Basic Hardware CPU Mouse Keyboard Video card RAM Network card Sound CardFloppy driveHard Disk driveZip driveUSB portsCD-ROM drive
12Stored Information Stores access/write code for keyboard Stores access/write code for system speakerStores access/write code for other chips (functions) on motherboardDoes not change (more on this in a moment)
13CMOS Complimentary Metal Oxide Semiconductor – how it was made Stores specific information about your system:Amount of RAM presentType of hard disk driveDate and TimeNeeds battery power to “remember” when power is off
15BIOS - Basic Input Output System All devices need BIOS code to interoperate with CPU. Some is stored directly in System BIOS chip, most is stored elsewhere.One of the functions of BIOS is to provide the CMOS Setup Utility, or Setup, which allows us to change CMOS data.
17CMOS or SetupOption to use this program is early in the boot cycle – long before system loads Operating SystemDifferent key(s) to enter different SetupsYou should only get to Setup on purposeProgram stored in BIOS, but only edits data in CMOSFirst CMOS was set of switches!
20Who makes BIOS? Award Software Phoenix Technologies AMI – American Megatrends Inc.They write BIOS with lots of options; motherboard maker picks sections to be usedLong gone are IBM’s patents on BIOSSame parent company
21Setup Lots of screens and subscreens You don’t need to know about all settings on all screensMotherboard book is mildly helpful on some optionsYou should know generally where things can be found
22Date and Time and … Usually on the first screen, or first menu choice Lets you set Date, Time, floppy present (will autodetect it), memory count, hard drive(s) present (again, autodetected)
30Chip EvolutionEPROM – Erasable Programmable ROM; used ultra-violet light (sunlight) to eraseEEPROM – Electrically Erasable – what we use todayFlash ROM – another name for EEPROMNVRAM – Non-volatile RAM. Really not so, still needs battery power
31The Three-In-OneWe have BIOS that stores code and access program to CMOSWe have CMOS that stores changeable information about our systemWe have RTC (Real Time Clock) that keeps track of date and timeAll three are now rolled into one chip
32About that Battery Should last 5 to 10 years You can find them at Savon evenIf your system forgets date and/or time, it’s time to replace the batteryBeware the evil ESD!
33More Battery Sometimes we WANT to reset CMOS: A forgotten passwordToo aggressive overclockingIncorrect low-level settings on some screenEither move the jumper, or pull the batteryDo either for about 10 secondsIf you are to pull battery, make sure you unplug system too
35More BIOS Option ROM – put a BIOS chip on the card/device Video is most common for thisSCSI cardsNetwork cards have socket, chip is extra
36Power On Self Test (POST) First thing to run when you start up computerWaits for “power good” signal from power supply, then starts the CPUFFFA is (almost) at the end of 1st meg of RAM, contains a “Jump Immediate” instruction to beginning of POST codeCPU instructs our “short list” items to check themselves out with own diagnostic
37POST, cont.Until video card is done, we are “in the dark” and could get “Beep Codes” for errors. Don’t memorize them. Constant beeping is either memory or video error.Once the video card has checked itself out, we could get error codes/messages on the monitor as other devices report status5
38POST, cont.About this time, we get the option to run CMOS Setup routinePOST is done; control passes to “Bootstrap Loader.” It’s job is to find OS.Looks for the “Boot Sector” on floppy/hard disk drive(s)A disk with functional OS is called a “Bootable Disk” or “System Disk.” Could be floppy (DOS), CD or hard disk drive.
39Boot OrderSomewhere in CMOS Setup is the ability to set the boot order, or the order in which the bootstrap loader will search for an OS.I set my systems to: CD/DVD drive, floppy and then hard disk drive.Usually, if a bootable CD is found, you get the option to boot from it (by pressing any key). Do nothing and loader continues the search for an OS.