The primary pathway between the CPU and [memory](Memory/Basics.md). It comprises the **data bus** that transfers data from the memory to the CPU and the **address bus** which transmits requests from the CPU to memory.
Main computer bus that determines data transfer rate speed and is the primary data transfer path between the CPU, RAM and other [motherboard](Motherboard.md) devices.
Transfers secondary cache (L2 cache) data at faster speeds, allowing more efficient CPU operations
## Bus standards
### Parallel and serial transmission types
There is a distinction between buses that use serial and buses that use parallel transmission. They are distinguished by the way in which data in the form of bits is transferred from one point to another, along the bus.
Serial Transmission is the type of transmission in which a single communication link is used to transfer the data from an end to another. On other hand Parallel Transmission is the transmission in which multiple parallel links are used that transmit each bit of data simultaneously.
* Serial buses operate at greater [latency](/Hardware/Bus.md#latency) than parallel buses
## Latency
Latency means _delay_: the delay from the time the data is requested until the time it arrives. In the context of a microprocesser and buses a key locus of latency would be between the time a request takes to travel accross the system bus from the CPU to the memory.
// TODO: Add explanation of bandwidth in the context of Hertz
SCSI (Small Computer System Interface) and ATA (Advanced Technology Attachment) are used for hard drive devices (i.e. internal buses). USB (Univeral Serial Bus) and SATA (Serial Advanced Technology Attachment) are used for peripheral devices, keyboards and modem devices (i.e external buses).
