What's the Definition of a Data Bus?

A bus is the wires that send information around inside of a computer

Three generations of women cooking together in kitchenProfile of senior couple forecasting the way forward for future finance and investmentClose up of baby grabbing feetEarthquake Survivors Undertake Rehabilitation At Sichuan Provincial PeopleThe Women of Standing Rock ReservationThe Women of Standing Rock ReservationThe Women of Standing Rock ReservationNepal Plane CrashRelatives Gather at Oklahoma City Bombing MemorialNew York Farm Offers Horseriding Therapy For PTSD SufferersFor Some Returning US Troops, PTSD Is The New BattlefieldFor Some Returning US Troops, PTSD Is The New BattlefieldIraq War Vet Struggles With PTSDFort Hamilton Soldiers Attend PTSD ScreeningU.S. War Veteran And Family Cope With Post Traumatic Stress DisorderU.S. War Veteran And Family Cope With Post Traumatic Stress DisorderStormy Weather To Hit The UKMichael Jackson Court Case ContinuesMichael Jackson Court Case ContinuesWoman in nightclub throwing beverage in man's faceCrowds Flock To Notting Hill For 2011 CarnivalCrowds Flock To Notting Hill For 2011 Carnival23rd Anniversary Of 1993 WTC Bombing Commemorated At 9/11 MemorialVermont Battles With Deadly Heroin EpidemicVermont Battles With Deadly Heroin Epidemic Getty Images Close-Up Of Fiber Racks : Stock Photo Comp Save to Board Close-Up Of Fiber Racks

Alex Tihonovs / EyeEm / Getty Images 

In computer parlance, a data bus—also called a processor bus, front side bus, frontside bus or backside bus—is a group of electrical wires that sends information (data) between two or more components. The Intel processor in the current line of Macs, for example, uses a 64-bit data bus to connect the processor to its memory.

Bus Width

A green computer hardware printed circuit board (PCB) with a closeup of a processor
Catalin Lungu / EyeEm.

A data bus has many different defining characteristics, but one of the most important is its width. The width of a data bus refers to the number of bits (electrical wires) that make up the bus. Common data bus widths include 1-, 4-, 8-, 16-, 32-, and 64-bit.

When manufacturers refer to the number of bits a processor uses, such as “This computer uses a 64-bit processor,” they are referring to the width of the front side data bus, the bus that connects the processor to its main memory. Other types of data buses used in computers include the backside bus, which connects the processor to the dedicated cache memory.

A data bus is typically governed by a bus controller that regulates the speed of information between components. Generally, everything needs to travel at the same speed within a computer and nothing can travel faster than the CPU. Bus controllers keep things moving at the same speed.

Early Macs used a 16-bit data bus; the original Macintosh used a Motorola 68000 processor. Newer Macs use 64-bit buses.

Types of Buses

A data bus can operate as a serial or a parallel bus. Serial buses—like USB and FireWire connections—use a single wire to both send and receive information between components. Parallel buses—like SCSI connections—use many wires to communicate between components. Those buses may be internal to the processor or external, relative to a given component being connected.