Purdue University - RHIT Department Memory u RAM is stored on internal microchips on-line RAM u ROM (Read only Memory) ROM –Stored permanently on chips in the computer –Usually not altered or erased. –Gives the computer its instructions when turned on –Contains the BIOS-Basic input/output System, amongst other things, which tells your computer how to operate and allows the software to take over.BIOS

Purdue University - RHIT Department Computer Memory u Memory refers to data stored on microchips, storage refers to data stored permanently on disk, tap, CD - etc. A more definitive definition of Memory vs StorageMemory vs Storage u Early systems had 640K of RAM which was primarily reserved for DOS, this is sometimes termed base memory which is up to 1MB. u Current systems still reserve 640 K of RAM for DOS, as well as other functions such as keyboard buffer and video memory. u There are many different types of RAM that have evolved to serve various purposes. This link provides a RAM guideThis link provides a RAM guide

Purdue University - RHIT Department Computer Memory u Primary Storage (System Memory) –RAM (Random Access Memory) - on line »Short Term - lost when computer is turned off »Limited in amount available »Very fast, random access to information u Dynamic Ram (DRAM) –Cheaper type of Memory chip - pretty slow –Access time to chip measured in nanoseconds »Chip name -12=120 nano. -7=70 nano. –If CPU runs faster than memory you have problems »Takes at least two clock cycles to refresh memory »Wait states for DRAM

Purdue University - RHIT Department Cache Memory CachingCache u Caching techniques avoid wait states. u A block of high speed RAM, typically Static RAM (SRAM) placed between the CPU and ordinary RAM u Cache Controller keeps likely needed data in Cache memory for high speed access. u Larger the cache memory, the more likely that the needed data will be available u Typical cache today is 64K K but can be higher u Primary cache or (L1) is in the CPU chip (typically 16K) Secondary Cache memory is external up until the P6.

Purdue University - RHIT Department Mass Storage u Secondary Storage (Mass Storage) –Permanent storage and retrieval ability –Very large capacity –Not as fast as on line memory u Hard, Floppy, Zip disks, tape, CD-ROM Cartridge –Sequential and Random Access Media

Purdue University - RHIT Department Hard Drives u Speed influenced by: –How fast the drive spins ( ,000 rpm) –Average Access (Seek) Time (5-8 milliseconds) –Data Transfer Rate-measured in MB/Sec. 80+ Mb/Sec. Depending on the interface. –SCSI fastest and can be daisy chainedSCSI u Storage Capacity –Used to be constrained to.5 GB by DOS 5/6 and BIOS –Interfaces such as ATA (.5 GB max), SCSI and IDE drives were not limited but had be partitioned. –Windows 95 allowed 2 GB, Windows 98 - no limit –More is better - typically 4 GB +

Purdue University - RHIT Department Floppy Drives –Floppy Drives (3.5" and 5.25" Disk Drives) »3.5" Disk Drive (High density = 1.44MB Medium = 720K) »5.25" Disk Drive (High Density = 1.2MB Double = 540K) –Formatting Floppy Disks »Format a: formats disk to capacity of drive »Format a: /f:720 formats medium density »incorrect format will mess up your disk –Write protect –Disk Care –Floptical Disks up to 230Mb, Zip Disks 100MB +FlopticalZip

Purdue University - RHIT Department Input / Output Devices u Input devices –Keyboards 84 keys old std. 101 is current –Mouse (Serial Port) –Light Pens –Touch Screen –Voice –Joy Stick –Scanners –Video/Camera –Modem?

Purdue University - RHIT Department Output Devices u Output Devices u Monitor (soft copy) CRTCRT –MDA - Monochrome Display Adapter (2 colors) –CGA - Color Graphics Adapter -RGB- (16 colors) –EGA - Enhanced Graphics Adapter (64 colors) –VGA - Video Graphics Array (256 & up) & SVGAVGA u Prior to VGA video signal was digital, almost all VGA is no analog u Pixels - Resolution (640X480 to 1280X1024)

Purdue University - RHIT Department Output Devices continued u Standard is SVGA X 600, 1024x768 –Influences on speed are memory, horizontal (kHz) and vertical scan rate (Hz) Refresh rate (Hz), interlacing,memory(Hz)Refresh rateinterlacing –VESA tries to establish video standardsVESA –3D Video Accelerators AGP3D Video AcceleratorsAGP u Printers –Impact Printers - dot matrix (9 and 24 pin); daisy wheel –InkJet - better image resolution but slow –Thermal - specialized application –Thermal transfer (wax) - best color printers –Laser dpi

Purdue University - RHIT Department Communication PortsPorts u Serial Ports - Com Port, RS-232C Serial –One lane wide - turns 8, 16, 32 wide path into 1 –Speed measured in BPS ,200 potential to go as high as 1 mill. in near future. –Usually used for modems and some printers u Parallel Ports Parallel –8 lanes wide - Lpt ports –Most commonly used for printers but with bi-directional other connections are possible –Up to 100 times faster than serial

Purdue University - RHIT Department Overview Of Hardware Components

Purdue University - RHIT Department Windows 98 Operating System u DOS - Where we came from –How to get around –Formatting disks –Copying files –Some basic commands –File and directory structure