2/6: CPUs & Memory CPUs –Parts of a sample CPU –Types of CPUs available ROM RAM –different kinds & uses inc. VRAM, SRAM image courtesy of How Computers Work CD

The CPU CPU terms –capacity, -bit –clock speed, MHz –CISC, RISC CPU brands & models image courtesy of AMD.com

CPU: Central Processing Unit The Microprocessor or CPU (Central Processing Unit) is the “brains” of the computer. All other components (RAM, monitor, disk drive) act like bridges to link you & the processor. image courtesy of AMD.com

Coprocessors Coprocessors are also in PC’s. They handle functions like graphics, 3-D acceleration, and sound cards. Help reduce the load on the main processor. image courtesy of How Computers Work

Data Capacity refers to the amount of data that the processor can process at one time. If a number is bigger than what the processor can handle, it breaks it down into manageable parts, processes it, and puts it back together. 8 bit processor: handles numbers up to 8 bits long (2 to the 8th power: 256) 16 bit processors handle numbers up to 2 to the 16th power or 65,536) 32, 64 bit processing (etc.)

Clock Speed Timer that everything in the processor uses as a pacesetter. Measured in MegaHertz (millions of cycles per second) Same model of processors can have their clock speeds compared. Different models of processors cannot be compared so easily. image from

Instruction Sets A chip’s vocabulary. Types of instructions that a chip can perform. Bigger does not necessarily equal better in instruction sets. CISC: Complex instruction set chips –use complex instructions to process instructions. RISC: Reduced instruction set chips –break down instructions before processing with a simpler instruction set. !

Types of chips: Intel Intel Pentium 4 – specsspecs –Up to 2.20 GHz –Rapid execution engine Intel Pentium III - specsspecs –up to 1.33 GHz –70 new instructions for 3D, voice recognition, etc. –integrated 256 KB L2 cache Intel Celeron - specsspecs –economy chip –up to 1.30 MHz –integrated 128 KB L2 cache images courtesy of TigerDirect.com, Intel

Types of chips: AMD AMD Athlon XP - specsspecs –Designed for Windows XP, (works w/ other OS’s) –Up to 1.67 GHz (but runs faster than Pentium GHz) –integrated 256 KB L2 cache –266 MHz system bus AMD Athlon - specsspecs –up to 1.4 GHz –integrated 256 KB L2 cache –266 MHz system bus AMD Duron – specsspecs –economical –up to 1.3 GHz –128 KB L1 cache, 64 KB L2 cache images courtesy of AMD

Types of Chips: Other Brands Cyrix MII Motorola PowerPC Apple Sun Digital others available images courtesy of Sun

ROM? RAM? Both refer to chip-based memory hardware –(not hard drives, CD-ROMs, etc.) ROM: Read-Only Memory –doesn’t change (much if at all) –BIOS stored here. RAM: Random Access Memory –changes frequently –short-term memory

ROM: Read-Only Memory Chips hardwired with start-up instructions Non-volatile –not dependent on electrical power to store information Necessary to start up the operating system (OS) Has a few options: disk drive boot order, etc.

RAM: Random Access Memory Synonyms: “main memory”, “primary memory”, “user memory” Dynamic memory –contents can be changed Why “random access”? –sequential access vs. random access –analogy: cassette vs. CD Programs, files stored here while in use. image courtesy of How Computers Work CD

How much RAM do you need? Current recommendation: 192 MB total RAM for a new computer Windows 98 uses ~ 20 MB of RAM Windows 2000 Pro uses ~ 95 MB of RAM McAfee Virus Scan & Task Manager ~ 7 MB MS Word uses ~ 7 MB MS Internet Explorer uses ~ 7 MB Each file you open is held in RAM, even after you close it

Varieties of RAM: DRAM DRAM: Dynamic RAM –volatile: needs electricity to hold data. Must be continually replenished with electricity. –SDRAM: Synchronous DRAM runs at the CPU clock speed (faster than prev. types) today’s main DRAM.

Variety of RAM: SRAM SRAM: Static RAM –static: does not need to be continually refreshed. –more expensive, bigger, and faster than DRAM. –used in CPU chips (caches) –used in “flash memory” image courtesy of Sonystyle.com