Lecture #29
- Announce
- Quiz Today
- Read Chapter 12, Computer Communications
Processing Technology
- Some Fundamental Limitations
- speed of light (length)
- heat dissipations (temperature)
- capacitance and inductance (delays)
- DC losses (Ohm's Law)
- AC losses (radiation)
- Other Important Concerns
- Economics !!! (cost)
- Noise
- Lifetime (mean time to failure)
- Space, weight (volume)
- Problems with Relay Computers
- speed
- power consumption
- reliability
- size & weight
- noise
- Vacuum Tube
- electronic switch
- how it works
- fast
- (Present day use of Vacuum Tubes)
- Televisions
- Computer Screens (when not LCD)
- Problems with Vacuum Tube Computers
- power consumption (filament always on)
- size & weight
- reliability
- noise (cooling)
- speed (~1/size)
- Transistor
- Two basic kinds (also N & P polarities)
- Junction Transistors/Bipolar Transistors
- Junction/Bipolar Transistors
- Historically First
- Size
- Current amplifiers
- Close to relays
- Current always flowing!
- Still uses much power
- Field Effect/Metal Oxide Semiconductor Transistors
- Field Effect/Metal Oxide Semiconductor Transistors
- How an MOS transistor works
- Voltage driven
- Almost no current (CMOS)
- Relate to relay (switch model)
- Integrated Circuits -- VLSI
- Multiple Transistors on a Chip
- Use photo-lithography to "print" wires and transistors
- SSI, MSI, LSI, VLSI
- Now get millions of transistors on 1/4 inch square chip
- Economics of Silicon (Micro-electronics)
- Tremendous cost to produce one chip
- If it works, extra copies almost free
- Do simulations of everything to get it right the first time
- Plant to produce memory chips costs ~$1 Billion
- CPUs in Everything
- Use programmed general purpose chips in place of
special purpose chips
- Programs in ROM (read-only memory)
- Technology Summary
- Measure of Computer Technology
| measure | speed | power/heat | weight | reliability MTF
|
|---|
| technology | (ops/s) | (mW/bit) | (kg/cpu) | (hours)
|
|---|
| relay | 100 | 10,000
| 100,000 | 1
|
|---|
| vacuum tube | 100,000 | 10,000
| 10,000 | 10
|
|---|
| transistor | 1,000,000 | 10
| 2,000 | 1,000
|
|---|
| early IC | 10,000,000 | 1
| 10 | 10,000
|
|---|
| current IC | 100,000,000 | 0.001
| 1 | 100,000
|
|---|
- Note: Assume computer equivalent to low cost PC in power
Note: All values are rough estimates
- Other Fascinating Technology Trails
- Displays (CRT, LCD, plasma)
- Printing (impact, laser, ink jet)
- Storage (tapes, disks)