Specifications

4–8 Functional Description
Subject to Change – 17 January 1997
PCI Devices
The bridge from the 21164 system bus to the 64-bit PCI bus is provided by the CIA
chip. It generates the required 32-bit PCI address for 21164 I/O accesses directed to
the PCI. It also accepts 64-bit double address cycles and 32-bit single address cycles.
However, the 64-bit address support is subject to some constraints. Refer to
Appendix A for more information on these constraints.
4.3.1 Saturn-IO (SIO) Chip
The 82378ZB SIO chip provides the bridge between the PCI bus and the ISA bus.
The SIO incorporates the logic for the following:
•
A PCI interface (master and slave)
•
An ISA interface (master and slave)
•
Enhanced 7-channel DMA controller that supports fast DMA transfers and
scatter-gather, and data buffers to isolate the PCI bus from the ISA bus
•
PCI and ISA arbitration
•
A 14-level interrupt controller
•
A 16-bit basic input/output system (BIOS) timer
•
Three programmable timer counters
•
Nonmaskable interrupt (NMI) control logic
•
Decoding and control for utility bus peripheral devices
•
Speaker driver
Refer to Intel document 82420/82430 PCIset ISA and EISA Bridges for additional
information.
4.3.2 PCI Expansion Slots
Four dedicated PCI expansion slots are provided on the AlphaPC 164. This allows
the system user to add additional 32-bit or 64-bit PCI options. While both the 32-bit
and the 64-bit slots use the standard 5-V PCI connector and pinout, +3.3 V is
supplied for those boards that require it. The SIO chip provides the interface to the
ISA expansion I/O bus.