Clocks - HP x4000 Technical Reference Manual

System Board
System Chipset

Clocks

Table 2-1 describes the clocks used in the x4000 Workstation.
Table 2-1
Name
System
Memory
Real Time
Clock (RTC)
Audio
Local Area
Network (LAN)
SCSI
Zircon
34
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Clocks
Description
A CK00-compliant clock synthesizer in a single
CKx_SKS clock chip creates the main system clocks
using a 14.318 MHz parallel mode crystal reference.
Two Direct Rambus Clock Generator (DRCG) chips
provide the clocks for the expansion channels to the
Memory Expansion Card (MEC). Using the 50 MHz
reference clock provided by the system clock
generator, each DRCG produces the 400 MHz
differential clock needed by the memory expansion
channel. The Memory Controller Hub (MCH)
provides two pairs of feedback signals to the DRCGs
to keep the Host and RDRAM clocks aligned.
A 32.768 KHz parallel mode crystal is the reference
for the ICH2 real-time clock circuitry.
A 24.576 MHz parallel mode crystal is the reference
for the Audio Codec.
A 25 MHz parallel mode crystal provides a
frequency reference for the 82550's internal
oscillator.
A 40 MHz oscillator provides the SCSI controller
SCLK.
A 10 MHz oscillator clocks the Zircon chip.
Chapter 2