1. CS 111 – Sept. 17 2.5 Beyond the CPU and memory
Peripheral devices
Communication speed
2.6 Making the CPU faster
Commitment:
Please read sections 3.1 and 3.2.
Quiz next Wednesday.

2. Devices & controllers
device = some peripheral plugged into computer, usually for I/O
controller = a circuit that allows a device to send data to/from CPU and memory.
device driver = program that knows how to use the controller. 2-way communication
memory mapped I/O = Program can access controller by referring to it with a memory address, as if it’s memory.
Direct Memory Access (DMA) = allow controller to load/store to memory while CPU is doing other work.
USB: technology allowing one controller to handle a variety of devices. Your machine has several USB ports.

3. Communication rate Used for both internal & network communication.
Units
“baud” = bit per second
Kbps, Mbps, Gbps
If there’s overhead/noise, figure on an average of 10 bits per byte, so 1 Mbps = 100 KB per second.
I can read a 20 MB file from USB drive in 2 seconds. What is the bit rate?
Voice telephone line – limited to 57.6 Kbps
DSL, cable modem: “broadband” times faster
Uses more of the sound spectrum; and data compression

4. Improving the CPU Pipelining Parallel or multi-processing
Run the instruction like an assembly line.
Partition the CPU: fetcher, decoder, executor
Fetch instruction #2 at the same time it decodes #1; etc.
Parallel or multi-processing
MIMD = “multiple instructions, multiple data”
Take a large task and give parts to different processors
A central “node” collects final answer.
SIMD = “single instruction, multiple data”
Good for: Small program, but a huge amount of data.
Each processor runs same program with small part of data.

5. Pipelining or not Without pipelining With pipelining F D X 1 2 3 F D X4 5 6 7