1. © 2000 Morgan Kaufman Overheads for Computers as Components System design techniques zPrivate branch exchange (PBX). zInk-jet printer. zPDAs. zSet-top boxes. zSystems-on-silicon.

2. © 2000 Morgan Kaufman Overheads for Computers as Components Digital telephone switches zHigh-end switches are highly reliable: y30 seconds downtime per year. zCompanies, homes install private branch exchanges (PBXs): yintercom features; ymanagement of long distance charges.

3. © 2000 Morgan Kaufman Overheads for Computers as Components Telephone switching systems zEstablish telephone calls: ywithin switch, find other phone line; youtside switch, find route to other line. zRoute voice samples between phones. zMeasure call time for billing. zProvide maintenance access to switch.

4. © 2000 Morgan Kaufman Overheads for Computers as Components Telephone terminology zLine: distinct telephone connection. zLine card: PBX/subscriber line interface. zOff-hook: active telephone. zOn-hook: inactive telephone. zTrunk line: phone lines between switches. zPOTS: plain old telephone service (analog, no fancy services).

5. © 2000 Morgan Kaufman Overheads for Computers as Components Computer-controlled telephone switching zVoice data rates: 8 bits sample ( or A law); 125 s period (8 kHz). zTelephones are I/O devices. zComputer bus is switch. CPU memory line card line card

6. © 2000 Morgan Kaufman Overheads for Computers as Components Dialing zDual-tone multi- frequency (DTMF): tones define row, column of key. zMust be held for 0.1 sec. 123 456 789 *0#

7. © 2000 Morgan Kaufman Overheads for Computers as Components Call states On-hook Rcv ringing Call Off-hook Dial tone Dialing Place ringing Receive call Place call Incoming call Take off-hook Return on-hook Take off-hook Dial decoder ready Number complete Other phone off-hook Line 1 Line 2

8. © 2000 Morgan Kaufman Overheads for Computers as Components PBX model zCalls are parallel processes: Call coordination, billing, etc. Call 1Call n...

9. © 2000 Morgan Kaufman Overheads for Computers as Components Tigerswitch system architecture zPC platform. ySwitch calls over ISA bus. zLine cards are custom devices.

10. © 2000 Morgan Kaufman Overheads for Computers as Components DTMF sensing zSoftware process on CPU. yUses lots of CPU time. zAnalog filter bank on line cards. yExpensive in volume. zDSP on separate card. yRequires new design. CPU memory line card line card DTMF card

11. © 2000 Morgan Kaufman Overheads for Computers as Components Switching zProcess-per-call is bad implementation. Context switch per call per 125 s. zUnroll calls into one loop. yEach loop iteration is one call for one sample. for (i=0; i<n_calls; i++) { /* from 1 to 2 */ data = read(call[i].line1); write(call[i].line2,data); /* from 2 to 1 */ data = read(call[i].line2); write(call[i].line1,data); }

12. © 2000 Morgan Kaufman Overheads for Computers as Components HP DesignJet drafting plotter zPlots up to 36 inches wide at 300 DPI. zCombines a variety of tasks: yhost communication; ygraphics language interpretation; yrasterization; ydevice control.

13. © 2000 Morgan Kaufman Overheads for Computers as Components The plotting process HP-GL/2PostScript rasterizer raster memory plotter controller

14. © 2000 Morgan Kaufman Overheads for Computers as Components Design considerations zMemory utilization is important. y36 inches X large X 300 DPI X n bits/pixel is a lot of memory. yRequires clever algorithms to minimize raster memory requirements. zRequires real-time control. zRequires concurrency: read new data, rasterize, control print head.

15. © 2000 Morgan Kaufman Overheads for Computers as Components HP DesignJet hardware architecture i960KA adrs latch bus if 1 MB ROM 2 MB DRAM proc. support ASIC || if RS- 422 pen ctrl ASIC swath RAM servo proc. (8052) EEPROM DRAM ctrl front panel stepper motor carriage PC board

16. © 2000 Morgan Kaufman Overheads for Computers as Components Early architectural decisions zChose Intel 80960KA as main processor. yHandled parsing, rasterization control, print engine control. yMultiplexed bus reduced pin count. yCould be upgraded to floating-point if necessary. zUsed modular I/O to host system. zDid not use disk for local storage.

17. © 2000 Morgan Kaufman Overheads for Computers as Components System components z2 MB RAM (SIMM sockets for more). zThree ASICs: ypen interface; yprocessor support; ycarriage. zServo processing performed by 8052 microcontroller.

18. © 2000 Morgan Kaufman Overheads for Computers as Components Rasterization zPlot is generated in swaths. ySeparate swath memory. zPixels are generated in row order by main processor. zPixels are fed to pens in column order. zPen interface ASIC transforms row order to column order.

19. © 2000 Morgan Kaufman Overheads for Computers as Components Data flows i960KA adrs latch bus if 1 MB ROM 2 MB DRAM proc. support ASIC || if RS- 422 pen ctrl ASIC swath RAM servo proc. (8052) EEPROM DRAM ctrl front panel stepper motor carriage PC board parsing and rasterization swath generation drawing

20. © 2000 Morgan Kaufman Overheads for Computers as Components Operations zServo processor controls stepper motor. zCarriage processor must write, read pen alignment marks. zProcessor support ASIC provides multiple functions: interrupt and mailbox communication. zMotion controller decodes position of print carriage and paper; watchdogs servo.

21. © 2000 Morgan Kaufman Overheads for Computers as Components Pen interface ASIC zInterfaces to i960 bus, swath memory, carriage ASIC. zPen interface reads pixels from swath in predetermined pattern using pixel address generator. zMust support bidirectional printing since head prints both ways.

22. © 2000 Morgan Kaufman Overheads for Computers as Components Carriage ASIC zInterrfaces to processor bus, pen interface ASIC, servo controller. zReads timing control registers using the CPU bus. zDelay registers add correction for pen alignment.

23. © 2000 Morgan Kaufman Overheads for Computers as Components Development process zPixel shuffling algorithm for pen interface/carriage ASICs was prototyped in C. zBuilt emulators for ASICs to allow parallel development of i960 software and hardware.

24. © 2000 Morgan Kaufman Overheads for Computers as Components Software development environment zPlotter software could be run on Unix workstation or target platform. yDiffered in I/O and print engine subsystems. yPrint engine was emulated on host with X window interface showing swath state. zUsed in-house RTOS. zHP-GL/2 parser was legacy code.

25. © 2000 Morgan Kaufman Overheads for Computers as Components Software development environment, contd. zRewrote vector/raster converter from assembly language to C to port to i960. zUsed gdb960 as monitor debugger on target system, communicating with host. zFront panel developed on PC, tested by user interface designers, marketing. zPaper loading designed by mechanical engineers.

26. © 2000 Morgan Kaufman Overheads for Computers as Components Personal digital assistant zPDA: portable, specialized information device. zCharacteristics: ylow cost for consumer market; yphysically small; ybattery-powered; ysoftware-rich.

27. © 2000 Morgan Kaufman Overheads for Computers as Components Apple Newton zFirst modern PDA. zOriginal used ARM 610; later version used StrongARM. zSupport operations in Runt ASIC: DMA, real-time clock, video interface, audio, PCMCIA. zSoftware written in NewtonScript language.

28. © 2000 Morgan Kaufman Overheads for Computers as Components Newton hardware architecture ARM 610ROMRAM Runt ASIC LCD speaker serial I/F A/D tablet PCMCIA infrared

29. © 2000 Morgan Kaufman Overheads for Computers as Components Motorola Envoy hardware architecture PCMCIA1 MB DRAM4 MB flash Astro system ASIC 68439 CPU audio modem infrared power supply A/D touchscreen Magicbus

30. © 2000 Morgan Kaufman Overheads for Computers as Components Feature creep zDesigners tend to add features to system during design. yIncreases power consuption. yChanges mechanical design. yMakes software design more complex. zSoftware thrashing can reduce battery life.

31. © 2000 Morgan Kaufman Overheads for Computers as Components PDA power supply zSystem must be designed to gracefully handle low battery power. yAbrupt power loss can destroy lots of data in RAM. zSmart Battery System puts electronics in battery to measure battery performance.

32. © 2000 Morgan Kaufman Overheads for Computers as Components InfoPad zBrodersen et al: advanced networked multimedia information appliance. zSystem performed many functions on remote systems to increase battery life. zMade use of specialized hardware units to reduce power consumption over software implementation.

33. © 2000 Morgan Kaufman Overheads for Computers as Components InfoPad hardware architecture Wireless network interface Speech codec Video decompressor ARM 60 display Keyboard/pointer other I/O

34. © 2000 Morgan Kaufman Overheads for Computers as Components Set-top boxes zInterface between cable/satellite and TV: ydigital television; yuser interface; ymay include back channel for purchases, etc. zVery cost-sensitive market.

35. © 2000 Morgan Kaufman Overheads for Computers as Components Set-top box in system set-top box IR digital TV input back channel

36. © 2000 Morgan Kaufman Overheads for Computers as Components Philips fiber-to-curb box hardware Network interface MPEG demux MPEG audio MPEG video NTSC CD-I graphics PCMCIA DRAM I/O kbd IR card NVRAM DRAM

37. © 2000 Morgan Kaufman Overheads for Computers as Components Fiber-to-curb box software default appscustom apps OS-9 kernelI/O manager device drivers boot/monitor software MPEG2 demux audio/video interfaces CD-I graphics network interface processor hardware layer OS layer application layer

38. © 2000 Morgan Kaufman Overheads for Computers as Components Systems-on-silicon zCan build significant embedded systems on single chip: yone or more high-performance CPUs; yI/O devices; ymemory. zAdvantages: yhigher performance and lower power; ylower cost.

39. © 2000 Morgan Kaufman Overheads for Computers as Components Moores Law (Sematech) 10 8 10 9 20002012 PC on chip billion-transistor system-on-chip

40. © 2000 Morgan Kaufman Overheads for Computers as Components Design challenges zCore-based design: cant take time to design gates, lines of code. zCustom architectures: yheterogeneous multiprocessors; ycustom memory systems. zVerification: ylong turnaround time; ycant probe interior directly.