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 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

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

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

Hard disk 2-20 Platters 3600-7400 RPM 1-10 Inch Diameter 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 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 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 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 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 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 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 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 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 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)

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 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 $$$$

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 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 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