So have been reading up on data buses, address buses and control buses and I understand what they do, but am confused about where they can physically be found. Some books/sites I have found state that they are inside of the CPU, some state that they transmit data all over the computer. E.g. the control bus can send signals to any other device within the computer, but then another book states that the control bus is inside of the CPU and synchronises the components of the CPU.

Can anyone help clarify this please?

  • \$\begingroup\$ Locate a CPU, locate the RAM. The traces in between are mostly the buses. \$\endgroup\$ – Eugene Sh. Nov 17 '15 at 18:44
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    \$\begingroup\$ Question should be closed - any CPU data sheet will have the answer. \$\endgroup\$ – Leon Heller Nov 17 '15 at 18:59

Data, Address and Control buses connect all of the 'subsystems' of a computer.

Address+Data+Control will connect the processor chip to external Memory and Peripheral Interfaces which will be contained in separate modules or chips on a laptop, desktop PC or server motherboard.

Peripheral Interfaces are the electronics which talk to the physical world, such as the CPU's view of SATA, Ethernet, Video-control, USB, WiFi, etc.

Address+Data+Control will connect to features internal to a CPU chip. For example on higher-end processors, features would include the cache controller or memory control. Hence those groups of signals are both within the chip, and across the motherboard (Printed Circuit Board, or PCB)

There may be some confusion caused by Microcontrollers. These chips contain the CPU, memory (flash and RAM), and Peripheral Interfaces within the chip. Further, many families of chips do not expose any of the internal Address, Data or Control signals. So descriptions of Microcontrollers may say that Address, Data and Control are only within the chip.

  • \$\begingroup\$ Additionally, some communication systems between chips might multiplex the address and data on the same wires. Or transmit both serially over a small number of wires. Or do any other weird combination. But conceptually the three busses stil exist :) \$\endgroup\$ – Wouter van Ooijen Nov 17 '15 at 21:58
  • \$\begingroup\$ @WoutervanOoijen - Agreed. Their may be some hardware optimisation to carry signals, but that is still conceptually the three buses. Do you think it's worth editing the answer to add that point? \$\endgroup\$ – gbulmer Nov 18 '15 at 11:08
  • \$\begingroup\$ No, I was just pre-empting possible nitpickers ;) \$\endgroup\$ – Wouter van Ooijen Nov 18 '15 at 16:06

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