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.

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.

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” 50-100+ times faster Uses more of the sound spectrum; and data compression

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.

Pipelining or not Without pipelining With pipelining F D X 1 2 3 F D X 4 5 6 7