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I/O Devices. Connected to the Backplane bus Hard disk controllers Graphics adapters Serial I/O Sound Cards Virtual Reality Helmet Gloves Quake controller. I/O Performance. I/O Bandwidth How much data can we move from A to B/time unit How many I/O operations can we perform/time unit

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i o devices
I/O Devices
  • Connected to the Backplane bus
    • Hard disk controllers
    • Graphics adapters
    • Serial I/O
    • Sound Cards
    • Virtual Reality
      • Helmet
      • Gloves
      • Quake controller
i o performance
I/O Performance
  • I/O Bandwidth
    • How much data can we move from A to B/time unit
    • How many I/O operations can we perform/time unit
  • Latency per access
    • Low long do we have to wait to get access
  • Response time
    • The total time to perform a task
disk i o performance
Disk I/O Performance
  • Supercomputer Benchmarks
    • Batch jobs
      • Large files
      • Throughput of data
  • Transaction Processing
    • I/O Rate
      • Many small accesses
  • File System
    • MakeDir, Copy, ScanDir, ReadAll, Make
types of i o devices
Types of I/O Devices
  • Behavior
    • Input, Output, Storage
  • Partner
    • Human/Machine
  • Data Rate
    • Human
      • Keyboard, 10b/sec
      • Voice, 100kb/sec
    • Hard Disk
      • 10Mb/sec
hard disk
Hard disk

1-10 inches

  • 2-20 Platters
  • 3600-7400 RPM
  • 1-10 Inch Diameter
  • 500-2000 tracks/surface
  • 32-128 sectors/track
  • Cylinder
    • All tracks at one position

2-20

Sectors

Track

hard disk6
Hard Disk
  • Average Seek Time (average time to move a track)
    • 8-12 ms
    • Does not consider locality
  • Rotational Latency
    • 4-8 ms
    • Often dominates over Seek Time
    • Start reading to ring-buffer when track reached
  • Transfer Rate
    • 2-10 Mb/sec

30

31

32

1

2

3

other properties
Other Properties
  • Storage Size 500Mb-10Gb
  • Cylinder 0, Boot Block
  • Partition Information
    • Usually a Physical Disk is devided into Smaller Partitions
    • File System Information
  • File System
    • The “data structure” for storing files and folders
    • Usually Hierarchical
      • Folders, sub folders and files
      • File types, (program/data-format) and protection bits
scsi eide i o bus
SCSI/EIDE I/O Bus
  • SCSI
    • General purpose interface for HDs, Scanners, Streamers, etc
    • Both synchronous/asynchronous operation
    • 5Mb/sec (standard SCSI higher for wide and ultra-wide)
    • 7 Devices/Bus Mastering/Self Selection Arbitration
  • EIDE
    • HDs and HD like devices (CR-ROMs etc)
    • Synchronous
    • 5Mb/sec
    • 2 Devices on each controller
    • HD controller on Interface
networks
Networks
  • RS-232, copper wire 19.2kbit/sec
    • Serial Point to Point Protocol (ppp)
  • LAN (Local Area Network), coaxial 100Mbit/sec
    • Ethernet 10Mbit/sec
    • Package 128-1530 bytes
    • Actually a bus with collision detection
  • Long Haul Network, fiber 1Gbit/sec
    • ARPANET (US government) became INTERNET
    • Packet Switched Networks
network file system
Network File System
  • Mounting Devices over the Network (usually LAN)
  • Local and Network devices transparent to User
  • Network Server - Local Client (a protocol)
  • Needs support by the OS
    • Local TCP stack, handles streams of I/O
    • Network Server forwards these streams
    • “Samba Server” makes Unix devices available to PCs
graphics adapters
Graphics Adapters
  • Each pixel uses a bit array (1-24bits)
  • 1280*1024*24bits/pixel needs approximately 4Mb

Red

Green

Blue

Yellow

White

8 + 8 + 8 =24bits/pixel

graphics adapter design
Graphics Adapter Design
  • Needs to update the Screen 60-100 times/sec (frames)
  • At 80Hz*4Mb=320Mb/sec Huge Throughput
  • We use special VRAM (Video RAM)
    • Shifts out bits to DAC at this high rate
  • Usually contain a Graphics Accelerator, which
    • Move and Copy Blocks of data in local VRAM
    • Perform operations, like AND/EXOR (bit mask)
    • Functions Line, Polygon Fill
    • “3D” functions like:
      • Polygon Shading, Texture Mapping etc.
video application example
Video Application Example
  • A system for real-time video recording/playback
    • A Frame Grabber, records video to HD
    • A Graphics Adapter displays video from HD
  • 640*480*8bits/pixel (256 colors)
    • 300kb/frame recording or playback
  • We do NOT want CPU in data path
approach 1
Approach 1
  • The Frame Grabber records one Frame (300kb) to local buffer
    • Frame Grabber gives interrupt
  • The OS sets up a DMA transfer from FG to RAM
    • The DMA gives interrupt
  • The OS sets up a DMA transfer to HD
    • The DMA gives interrupt
    • The HD gives interrupt, data written to disk
  • At 25 frames/sec (TV quality) this gives
    • 2 (first to RAM then to HD) * 300 * 25 = 15Mb/sec

Hmm, no Good! A lot bus activity, too high HD throughput

(and this is for just recording)

approach 2
Approach 2
  • Put MPEG-2 hardware compression on the Frame Grabber, now only 30kb/frame
    • Frame Grabber gives interrupt
  • The OS sets up a DMA transfer from FG to HD
    • The DMA gives interrupt
    • The HD gives interrupt, data written to disk
  • At 25 frames/sec (still TV quality) this gives
    • 30 * 25 = 750kb/sec
  • Simultaneous record/playback gives
    • 1.5 Mb HD throughput, which is possible but still quite high
    • A lot of activity on the SCSI bus
approach 3
Approach 3
  • Frame Grabber
    • MPEG-2 hardware compression, now only 30kb/frame
    • Graphics Adapter, that can display MPEG-2 frames
    • SCSI bus to local HD for video storage
    • Interrupt each frame recorded, or finished playback sequence
  • Best solution! Almost no bus PC bus activity
  • You get what you pay for, this one will cost you $$$$
high fidelity audio
High Fidelity Audio
  • PCM 44.1 kHz 16bits Stereo (WAV/AIFF)
  • 96 db signal/noice ratio

16 bit

signed integer

Left

16 bit

signed integer

Right

sound cards
Sound Cards
  • Wave-Table playback
    • 16 bit (Stereo at 44.1 kHz)
    • 32 voices
    • 5.6 Mb/sec (quite high bandwidth)

WaveTable

ROM/RAM

Signal Processor

Audio

MIX

DA/Filter

...

audio i o
Audio I/O
  • In/Out
    • Data Buffers
    • DMA Channel
    • IRQ (Interrupt number) 2 IRQ for full duplex operation
  • 350kb/sec throughput on bus, OK

In Buffer

DSP

Filter/Ad

Audio In

Out Buffer

DA/Filter

Audio Out

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