1. I/O Devices Connected to the Backplane bus Hard disk controllers
Graphics adapters
Serial I/O
Sound Cards
Virtual Reality
Helmet
Gloves
Quake controller

2. I/O Performance I/O Bandwidth Latency per access Response time
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

3. Disk I/O Performance Supercomputer Benchmarks Transaction Processing
Batch jobs
Large files
Throughput of data
Transaction Processing
I/O Rate
Many small accesses
File System
MakeDir, Copy, ScanDir, ReadAll, Make

4. Types of I/O Devices Behavior Partner Data Rate Input, Output, Storage
Human/Machine
Data Rate
Human
Keyboard, 10b/sec
Voice, 100kb/sec
Hard Disk
10Mb/sec

5. Hard disk 2-20 Platters 3600-7400 RPM 1-10 Inch Diameter
1-10 inches
2-20 Platters
RPM
1-10 Inch Diameter
tracks/surface
sectors/track
Cylinder
All tracks at one position
2-20
Sectors
Track

6. 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 …

7. 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

8. SCSI/EIDE I/O Bus SCSI EIDE
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

9. 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 bytes
Actually a bus with collision detection
Long Haul Network, fiber 1Gbit/sec
ARPANET (US government) became INTERNET
Packet Switched Networks

10. 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

11. Graphics Adapters Each pixel uses a bit array (1-24bits)
1280*1024*24bits/pixel needs approximately 4Mb
Red
Green
Blue
Yellow
White
=24bits/pixel

12. Graphics Adapter Design
Needs to update the Screen 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.

13. 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

14. 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 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)

15. 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

16. Approach 3 Frame Grabber Best solution! Almost no bus PC bus activity
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 $$$$

17. 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

18. 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
...

19. Audio I/O In/Out 350kb/sec throughput on bus, OK 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