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4–6 Functional Description
ISA Bus Devices
The bridge from the 21164PC system bus to the 64-bit PCI bus is provided by the
21174 chip. It generates the required 32-bit PCI address for 21164PC 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.
4.2.4 PCI/ISA Bridge Chip
The CY82C693U-NC chip provides the bridge between the PCI and the ISA bus,
and between the PCI and the EIDE bus. It also incorporates the logic for the follow-
ing:
• Keyboard/mouse controller – An 8042-compatible interface is brought out to
separate 6-pin DIN connectors (J4).
• Real-time clock – A DS1287-compatible clock is backed up by a replaceable
battery (XB1).
• A PCI interface (master and slave).
• An ISA interface (master and slave).
• PCI and ISA arbitration.
Refer to the Cypress document CY82C693U hyperCache/Stand-Alone PCI
Peripheral Controller with USB Data Sheet for additional information.
4.2.5 PCI Expansion Slots
Four dedicated PCI expansion slots are provided on the AlphaPC 164SX. 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 CY82C693U-NC chip provides the
interface to the ISA expansion I/O bus.
4.3 ISA Bus Devices
Figure 4–4 shows the AlphaPC 164SX ISA bus implementation with peripheral
devices and connectors. Two dedicated ISA expansion slots are provided. System
support features such as serial lines, parallel port, and diskette controller are embed-
ded on the module by means of an FDC37C669 combination controller chip.