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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.
For example, an 8-bit-byte-addressable machine with a 20-bit address bus (e.g. Intel 8086) can address 2 20 (1,048,576) memory locations, or one MiB of memory, while a 32-bit bus (e.g. Intel 80386) addresses 2 32 (4,294,967,296) locations, or a 4 GiB address space. In contrast, a 36-bit word-addressable machine with an 18-bit address bus ...
The starting address must be 64-bit aligned; i.e. AD2 must be 0. The data corresponding to the intervening addresses (with AD2 = 1) is carried on the upper half of the AD bus. To initiate a 64-bit transaction, the initiator drives the starting address on the AD bus and asserts REQ64# at the same time as FRAME#.
A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent or read from, and a control bus to determine its operation. The technique was developed to reduce costs and improve modularity, and ...
MBus specifies a 64-bit datapath, which uses 36-bit physical addressing, giving an address space of 64 GB. The transfer rate is 80 MB/s sustained (320 MB/s peak) at 40 MHz, or 100 MB/s (400 MB/s peak) at 50 MHz. Bus controlling is done by an arbiter. Interrupt, reset, and timeout logic are also specified.
Bit transfers occur on both the rising and the falling edges of the clock, so the transfer rate is double the clock rate. Intel describes the data throughput (in GB/s) by counting only the 64-bit data payload in each 80-bit flit. However, Intel then doubles the result because the unidirectional send and receive link pair can be simultaneously ...
Learn how to download and install or uninstall the Desktop Gold software and if your computer meets the system requirements.
Devices are each mapped onto a 28-bit address space (256 MB). Only eight masters are supported, although there can be an unlimited number of slaves. When the 64-bit UltraSPARC was introduced, SBus was modified to support extended transfers of a 64 bits doubleword per cycle to produce a 200 MB/s 64-bit bus. This variant of the SBus architecture ...