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The simplest system bus has completely separate input data lines, output data lines, and address lines. To reduce cost, most microcomputers have a bidirectional data bus, re-using the same wires for input and output at different times. [20] Some processors use a dedicated wire for each bit of the address bus, data bus, and the control bus.
In computing, an input–output memory management unit (IOMMU) is a memory management unit (MMU) connecting a direct-memory-access–capable (DMA-capable) I/O bus to the main memory. Like a traditional MMU, which translates CPU -visible virtual addresses to physical addresses , the IOMMU maps device-visible virtual addresses (also called device ...
Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
Each device can request up to six areas of memory space or input/output (I/O) port space via its configuration space registers. In a typical system, the firmware (or operating system ) queries all PCI buses at startup time (via PCI Configuration Space ) to find out what devices are present and what system resources (memory space, I/O space ...
The 11/45 architecture expanded to allow 4 MB of physical memory segregated onto a private memory bus, 2 KB of cache memory, and much faster I/O devices connected via the Massbus. PDP–11/34 (1976 [ 15 ] ) and PDP–11/04 (1975 [ 15 ] ) – Cost-reduced follow-on products to the 11/35 and 11/05; the PDP–11/34 concept was created by Bob ...
Instead, A PCI device can request control of the bus ("become the bus master") and request to read from and write to system memory. More precisely, a PCI component requests bus ownership from the PCI bus controller (usually PCI host bridge, and PCI to PCI bridge [ 6 ] ), which will arbitrate if several devices request bus ownership ...
SBus is a computer bus system that was used in most SPARC-based computers (including all SPARCstations) from Sun Microsystems and others during the 1990s. It was introduced by Sun in 1989 to be a high-speed bus counterpart to their high-speed SPARC processors, replacing the earlier (and by this time, outdated) VMEbus used in their Motorola ...
Devices for communication between computers, such as modems and network cards, typically perform both input and output operations. Any interaction with the system by an interactor is an input and the reaction the system responds is called the output. The designation of a device as either input or output depends on perspective.