Intel 386 manual Multibus II Standard, Parallel System BUS iPSB

CHAPTER 10

MULTIBUS 'II AND Intel386 OX MICROPROCESSOR

Standard bus interfaces guarantee compatibility between existing and newly developed systems. This compatibility safeguards a user's hardware investment against obsoles- cence even in the face of rapidly advancing technology. The MULTIBUS I standard interface has proven its value in providing flexibility for the expansion of existing systems and the integration of new designs. The MULTIBUS II standard interface extends Intel's Open Systems design strategy into the world of 32-bit microprocessing systems.

10.1 MULTIBUS II STANDARD

The MULTIBUS II standard is a processor-independent bus architecture that features a 32-bit parallel system bus with a maximum throughput of 40 megahytes per second~

high-speed local bus access to off-board memory, a low-cost serial system bus, and full multiprocessing support. MULTIBUS II achieves these features through five specialized Intel buses:

•Parallel System Bus (iPSB)

•Local Bus Extension (iLBX II)

•Serial System Bus (iSSB)

•Multi-channel DMA 110 Bus

•System Expansion I/O Bus (iSBXTM)

The DMA I/O Bus and the. iSBX are carried over directly from MULTIBUS I architec- ture. See the MULTIBUS~ I Architectural Specification for a full description of these buses. The multiple bus structure provides the following important advantages over a single, generalized bus:

•Each bus is optimized fora specific function.

•The buses perform operations in parallel.

•Buses that are not needed for a particular system can be omitted, avoiding unneces- sary costs.

10.2PARALLEL SYSTEM BUS (iPSB)

The Parallel System Bus (iPSB) is optimized for interprocessor data transfer and com- munication. Its burst transfer capability provides a maximum sustained bandwidth of 40 megabytes per second for high-performance data transfers.

10-1