Systems Design and Programming DMA I CMPE 3101 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Disk Memory SystemsMagnetic and optical:• Floppy disks• Hard disks• CD-ROMs and WORMs (write once/read mostly)• DVDFloppy:Inner trackOutter trackSectorCommonly holdbetween 512 to1024 bytes of data.Systems Design and Programming DMA I CMPE 3102 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6FloppyOlder 5 and 1/4 flexable floppies spin at 300 RPM, have 40 tracks with 9 sec-tors/track and two sides.Capacity = 40 X 2 X 9 X 512 = 368,640 or ~360K bytes of information.Newer ones are high-density with 80 tracks and 15 sector/track for 1.2 MB.Heads actually contact the disk surface, leading to wear out.The recording format called MFM (modified frequency modulation) used towrite double density format.DC DC DC DCDCDCDC1 0 0 1 0 1 1Systems Design and Programming DMA I CMPE 3103 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6FloppyThe rules are given as follows: A data pulse is always stored for a logic 1. No data and no clock is stored for the first logic 0 in a string of logic 0s. The second and subsequent logic 0s in a row contain a clock pulse, but nodata pulse.The clock is inserted in subsequent 0s to maintain synchronization as data isread from the disk.The micro-floppy is much mor e popular today:Head slotHead doorWrite protectSystems Design and Programming DMA I CMPE 3104 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6FloppyAdvantages of the micro-floppy over the mini-floppy . Rigid plastic case provided better protection. Head door kept disk from being exposed. Write protection mechanism. Keyed mechansim for track 0. Increase in storage capacity:80 tracks X 2 sides X 18 sectors/track X 512 bytes/sector = 1.44 MB.Extended high density micro-floppy capable of 2.88 MB.A second extension is the floptical disk which stores data magnetically usingan optical tracking system.It stores 21 MB of data.Hard Disks:Use a flying head to stor e and read data from the platters and spins at3,000 to 10,000 RPM (> 10X that of floppies).Systems Design and Programming DMA I CMPE 3105 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Hard DisksHard disks usually have at least 4 platters and can have 2 heads per surface.The heads are moved from cylinder to cylinder using a voice coil.Hard disks use MFM or RLL (run-length limited) to store information.RLL 2,7 is common today -- this indicates that the number of zeros ina row is always between 2 and 7.plattersurfaceheadtracksectorcylinderSteppermotor orvoice coilSystems Design and Programming DMA I CMPE 3106 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Hard DisksThe data is first encoded using the table given below.Note that this encoding always guarantees at least 2 zeros and no morethan 7 zeros in a row.This encoding allows nearly a 50% increase in storage capacity over MFMswithout changing the driver electronics or disk surface.RLL drives increase the number of tracks from 18 to 27 to achieve this.40 MB -> 60 MB with better performance.Input Data Stream RLL output000 00010010 0100010 1001000010 0010010011 1000011 0010000011 00001000Systems Design and Programming DMA I CMPE 3107 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Hard DisksFor example, given the data stream 101001011:Although all disks use MFM or RLL, disk interfaces vary.Todays systems use ESDI (non-existent), SCSI (small computer systeminterface) and IDE (integrated drive electronics).IDE incorporates the disk controller in the disk drive and usually contain a 32KB cache.Access times are less than 10ms (compared with 200ms for floppies).1 0 1 0 0 1 0 1 1MFMRLL010 001 001 001 001 000Systems Design and Programming DMA I CMPE 3108 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Optical DisksCD-ROMs and WORMs store up to 660 MB of data.DVDs are similar but have much higher bit density (4.7, 8.5 and 17 GB).land pitLaserPhotodiodeLensesLensesTransparent, protectivelayerCD-ROMSystems Design and Programming DMA I CMPE 3109 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6Video DisplaysColor displays are extremely popular.Some accept informaton as a composite video signal (similar to TVs), asTTL voltage level signals (0 or 5V) and as analog signals (0 to 0.7V).Composites are disappearing since high-resolution cannot be achieved.They combine the color information with other information such as syncpulses.Most modern systems use direct vido signals with separate sync signals.Monochrome monitors use one wire for video, one for horizontal syncand one for vertical sync.Color monitors use three video signals, one for red, green and blue(RGB).The TTL RGB Monitor:It uses TTL level signs (0 or 5V) as video inputs and a 4th line calledintensity.It can display a total of 16 different colors (CGA in older systems).Systems Design and Programming DMA I CMPE 31010 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6TTL RGB MonitorThe following table gives the RGB values and colors:Cyan is a combination of Green and Blue, Magenta - Red and Blue, etc.Intensity Red Green Blue Color0 0 0 0 Black0 0 0 1 Blue0 0 1 0 Green0 0 1 1 Cyan0 1 0 0 Red0 1 0 1 Magenta0 1 1 0 Brown0 1 1 1 White1 0 0 0 Gray1 0 0 1 Bright Blue1 0 1 0 Bright Green1 0 1 1 Bright Cyan1 1 0 0 Bright Red1 1 0 1 Bright Magenta1 1 1 0 Yellow1 1 1 1 Bright WhiteSystems Design and Programming DMA I CMPE 31011 (May 5, 2002)UMBCU M B CUNIVERSITY OF MARYLAND BALTIMORE COUNTY1 9 6 6TTL and Analog RGB MonitorThe connector pin definitions for either color or monochromeHorizontal and vertical retrace are for synchronization.Normal video is used for “intensity” on monochrome monitors.Analog RGB MonitorsAnalog RGB monitors have 3 video signals (no intensity) that can bedriven with values between 0 and 0.7 V.Most can display 256K, 16M or 24M colors.59483 2 17 61 and 2: Ground3: Red video4: Green video5: Blue video6: Intensity7: Normal video8: Horizontal retrace9: Vertical retrace8157146 5 413 121: Red2: Green (mono)3: Blue4 and 5: GND9: Female is blocked10 and 15: GND11: Color detect (GND mono)311210196/7/8: RGB GND12: Mono detect (GND color)13: Horz sync14: Vert sync15: GNDSystems Design and Programming DMA I CMPE 31012 (May 5, 2002)UMBCU M B CUNIVERSITY OF