Table of Contents
Advertisement
4.4
SYSTEM CLOCK DISTRIBUTION
These systems use an Intel CK-type clock generator and crystal for generating the clock signals
required by the system board components. Table 4-6 lists the system board clock signals and how
they are distributed.
Table 4-6. Clock Generation and Distribution
Frequncy
100 or 133 MHz
66 MHz
48 MHz
33 MHz
14.31818 MHz
14.31818 MHz
Certain clock outputs are turned off during reduced power modes to conserve energy. Clock output
control is handled through the SMBus interface by BIOS.
4.5
REAL-TIME CLOCK AND CONFIGURATION MEMORY
The Real-time clock (RTC) and configuration memory (also referred to as "CMOS") functions are
provided by the ICH component and is MC146818-compatible. As shown in the following figure,
the ICH component provides 256 bytes of battery-backed RAM divided into two 128-byte
configuration memory areas. The RTC uses the first 14 bytes (00-0Dh) of the standard memory
area. All locations of the standard memory area (00-7Fh) can be directly accessed using
conventional OUT and IN assembly language instructions through I/O ports 70h/71h, although the
suggested method is to use the INT15 AX=E823h BIOS call.
Figure 4-5. Configuration Memory Map
A lithium 3-VDC battery is used for maintaining the RTC and configuration memory while the
system is powered down. The battery is located in a battery holder on the system board is replaced
with a Renata CR2032 or equivalent 3-VDC lithium battery.
Table 4-6
Clock Generation and Distribution
Source
Destination
CK
Processor, GMCH, DIMM sockets
CK
GMCH, ICH2, AGP slot
CK
GMCH, ICH/ICH2, I/O Cntlr.
CK
Processor, ICH/ICH2, PCI Slots
Crystal
CK
CK
ICH/ICH2, I/O Cntlr., and (on iPAQ 2.0) audio codec
Register D
0Dh
Register C
0Ch
0Bh
Register B
Register A
0Ah
Year
09h
Month
08h
Date of Month
07h
Day of Week
06h
Hours (Alarm)
05h
Hours (Timer)
04h
Minutes (Alarm)
03h
Minutes (Timer)
02h
Seconds (Alarm)
01h
Seconds (Timer)
00h
Compaq iPAQ Series of Desktop Personal Computers
Second Edition - February 2001
Technical Reference Guide
82801
FFh
Extended Config.
Memory Area
(128 bytes)
80h
7Fh
Standard Config.
Memory Area
(114 bytes)
0Eh
0Dh
RTC Area
(14 bytes)
00h
CMOS
4-11
Advertisement
Table of Contents
