-a way to transfer info/msgs between processor, memory and devices

-multi-bus systems are possible


-made of millions of transistors

-can exert bus lock to send info to memory (like intercom)

-asks devices for info

-in the old days, put info from disc to memory

-today, DMA (direct memory access) is possible

-clock rate= Ghz= millions of cycles per second

-instructions per cycle vs. clock rate

-RISK- reduced instruction set computers (fewer instructions, done faster)

-super pipelining- making pipe longer w/smaller task at each step


-polling- processor asks disc if task is complete

-interrupting- disk tells processor when it's done

-many disk/memory interactions, but only 1 msg is sent at a time


-cuts down on memory access

-stores info from memory sequentially

-is checked before memory

-cache is useless if memory is accessed randomly