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PCI Devices
Figure 4–2 Clock Distribution
Differential
PECL
MC12439
Outputs
166 MHz
167-MHz
+
PLL
-
X10
16.66-MHz
xtal
4.6 PCI Devices
The AlphaPC 264DP uses the PCI bus as the main I/O bus for the majority of periph-
eral functions. The board implements the ISA bus as an expansion bus for system
support functions and peripheral devices.
Table 4–1 shows the IDSEL assignment for all the PCI devices.
Table 4–1 IDSEL Assignments for PCI Devices
Device/PCI Bus Number
Cypress PCI/ISA /Bus 0
Slot 0/Bus 0
Slot 1/Bus 0
Slot 2/Bus 0
Adaptec PCI/SCSI /Bus 0
Functional Description
4–8
Differential
PECL
osc
frame
Control
(2V OD)
fwdclk
Divide
fwdclk
sysclk
by 1
166 MHz
fwdclk
sysclk
Divide
by 2
sysclk
83 MHz
3.3-V Control
fwdclk
sysclk
IDSEL Assignment
PCI0_AD16
PCI0_AD18
PCI0_AD19
PCI0_AD20
PCI0_AD17
12 February 1999 – Subject To Change
L2 Cache
Cache Address,
Control and Clocking
21264
Forwarded
Clocks
Forwarded
Clocks
Cchip
Dchips (8)
3.3-V Rail-to-Rail
CMOS Interface
3.3-V Data
pclk[7:0]
Pchips (2)
pciclk
Main Memory
PLL
SDRAM DIMMs
83 MHz
CPU to Cchip and
Dchip interfaces are
clock forwarded.
166-MHz clock is
used to clock data
on both edges.
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