User`s guide

U40 also generates two 33-MHz clock signals, which are distributed as shown
in Table 3–5.
Table 3–5 Distribution of 33-MHz Clock Signals
Clock Signal Name Destination
clk1_pal U25 (L2 cache PAL) (AlphaPC64.7)
clk1_fb U39 (provide feedback to S4402 PLL) (AlphaPC64.5)
There are two additional oscillators that provide 14.3-MHz and 24-MHz clocks
for the AlphaPC64, as shown in Figure 3–10.
Figure 3–10 Buffered Clock Distribution Network
LJ-04139.AI
82378ZB
PCI-to-ISA
Bridge
14.3-MHz
Oscillator
AlphaPC64.26
pciclk_sio
AlphaPC64.5
sysclk
ISA
AlphaPC64.36
8242
Keyboard
and Mouse
AlphaPC64.31
osc
ISA
ISA
clkb
kclk
mclk
A 14.3-MHz oscillator (69.9-ns period) (AlphaPC64.36) output is buffered and
produces osc, which is routed to the host PCI-to-ISA bridge (AlphaPC64.26)
and the three ISA slots (AlphaPC64.27). This is the standard 14.31818-MHz
ISA clock.
A 24-MHz oscillator (41.7-ns period) (AlphaPC64.36) produces osc24, which
provides clocking for the National 87312 combination chip (AlphaPC64.29).
Functional Description 3–29