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Functional Description 4–5
21174 Core Logic Chip
4.2.3 PCI Devices
The AlphaPC 164SX uses the PCI bus as the main I/O bus for the majority of periph-
eral functions. As Figure 4–3 shows, the board implements the ISA bus as an expan-
sion bus for system support functions and for relatively slow peripheral devices.
Figure 4–3 AlphaPC 164SX PCI Bus Devices
The PCI bus supports multiplexed, burst mode, read and write transfers. It sup-
ports synchronous operation of 33 MHz. It also supports either a 32-bit or 64-bit
data path with 32-bit device support in the 64-bit configuration. Depending upon
the configuration and operating frequencies, the PCI bus supports up to 264-MB/s
(33 MHz, 64-bit) peak throughput. The PCI provides parity on address and data
cycles. Three physical address spaces are supported:
• 32-bit memory space
• 32-bit I/O space
• 256-byte-per-agent configuration space
21174
CY82C693U-NC
Primary
J6
Secondary
J5
ISA EIDE
PCI
Slot 0
J19
PCI
Slot 1
J18
PCI
Slot 2
J17
PCI
Slot 3
J15
PCI
ISA Bus
Device IDSEL Select
Slot 2 16
Slot 0 17
Slot 1 18
PCI/ISA Bridge 19
Slot 3 20