The Micro Channel supports another mode of data streaming whereby the address bus can also be used to transfer data. This is depicted in Figure 9 on page 15.
Figure 9. Micro Channel - Data Streaming Transfer (80 MBps)
As can be seen from this figure, in this mode, after the initial address is presented during the first bus cycle, the address bus is then multiplexed to carry an additional 32 bits of data. This results in an effective data transfer rate of 80 MBps.
Data streaming, as well as improving the data transfer rate, also provides a more efficient use of the Micro Channel. Since MCA operations complete in a shorter amount of time, the overall throughput of the system is increased.
Data streaming is useful for any adapters that perform block transfers across the Micro Channel such as the IBM
MCA is implemented in some models of the IBM PC Server 300 and 500 lines and in all models of the PC Server 720.
1.5.4 PCI Bus
In the later part of 1992, Intel, IBM and a number of other companies worked together to define a new local component bus which was designed to provide a number of new features and work with a wide range of new processors. The result was the Peripheral Component Interconnect (PCI) bus. The PCI bus was designed to provide the Pentium processor with all the bandwidth it needed and to provide for more powerful processors in the future. It was also designed for use in multiprocessing environments.
The PCI bus was designed to work with a number of buses including Micro Channel, ISA and EISA buses. It was designed to provide a local bus, more tightly integrated with the processor, to provide more bandwidth to I/O devices such as LAN adapters and DISK controllers, which require more bandwidth than
Chapter 1. IBM PC Server Technologies 15
