1. 单总线结构：
在单总线结构中，一种公共总线用于在外围设备和微处理器之间进行通信。由于使用一根公共总线，它具有缺点。
2. 双总线结构：
在双总线结构中，一根总线用于获取指令，另一根总线用于获取执行所需的数据。就是要克服单总线结构的瓶颈。
单总线和双总线结构的区别：
| Single Bus Structure | Double Bus Structure |
|---|---|
| One common bus is used for communication between peripherals and processor. | Two buses are used, one for communication from peripherals and other for processor. |
| Instructions and data both are transferred in same bus. | Instructions and data both are transferred in different buses. |
| Its performance is low. | Its performance is high. |
| Cost of single bus structure is low. | Cost of double bus structure is high. |
| Number of cycles for execution is more. | Number of cycles for execution is less. |
| Execution of process is slow. | Execution of process is fast. |
| Number of registers associated are less. | Number of registers associated are more. |
| At a time single operand can be read from bus. | At a time two operands can be read. |