Intel Pentium 4 User Manual

I/O Controller Hub 2
R
158 Intel
®
Pentium
®
4 Processor / Intel
®
850 Chipset Family Platform Design Guide
9.8.2 External Capacitors
To maintain the RTC accuracy, the external capacitor C1 needs to be 0.047 µF, and the external
capacitor values (C2 and C3) should be chosen to provide the manufacturer’s specified load
capacitance (Cload) for the crystal when combined with the parasitic capacitance of the trace,
socket (if used), and package. When the external capacitor values are combined with the
capacitance of the trace, socket, and package, the closer the capacitor value can be matched to the
actual load capacitance of the crystal used, the more accurate the RTC will be.
Equation 9-1 can be used to choose the external capacitance values (C2 and C3):
Equation 9-1. External Capacitance Values
C
LOAD
= (C
2
* C
3
)/(C
2
+C
3
) + C
PARASITIC
Note: C3 can be chosen such that C3 > C2. Then C2 can be trimmed to obtain the 32.768 kHz.
9.8.3 RTC Layout Considerations
• Keep the RTC lead lengths as short as possible; around ¼ inch is sufficient.
• Minimize the capacitance between X
IN
and X
OUT
in the routing.
• Put a ground plane under the XTAL components.
• Do not route switching signals under the external components (unless on the other side of the
board).
• The oscillator VCC should be clean; use a filter, such as a RC lowpass, or a ferrite inductor.
9.8.4 RTC External Battery Connection
The RTC requires an external battery connection to maintain its functionality and its RAM while
the ICH2 is not powered by the system.
Example batteries are: Duracell* 2032, 2025, or 2016 (or equivalent), which can give many years
of operation. Batteries are rated by storage capacity. The battery life can be calculated by dividing
the capacity by the average current required. For example, if the battery storage capacity is
170 mAh (assumed usable) and the average current required is 3 uA, the battery life will be at
least:
170,000 uAh / 3 uA = 56,666 h = 6.4 years
The voltage of the battery can affect the RTC accuracy. In general, when the battery voltage
decays, the RTC accuracy also decreases. High accuracy can be obtained when the RTC voltage is
in the range of 3.0v to 3.3v.

Intel Pentium 4 Specifications

General

Architecture	x86
Core Count	1
Microarchitecture	NetBurst
Manufacturer	Intel
Core Names	Willamette, Northwood, Prescott, Cedar Mill
Virtualization Technology	No
Release Date	November 20, 2000
Clock Speed	1.3 GHz to 3.8 GHz
FSB Speed	400 MHz to 1066 MHz
Socket	Socket 423, Socket 478, LGA 775
Introduced	2000
Product Line	Pentium
Front Side Bus	400 MHz to 1066 MHz
Hyper-Threading	Yes (Prescott and later)
64-bit Support	Yes (Prescott and later)
Instruction Set	MMX, SSE, SSE2, SSE3
Discontinued	2008
Process Technology	180 nm, 130 nm, 90 nm, 65 nm
L2 Cache	256 KB, 512 KB, 1 MB, 2 MB
Lithography	180 nm, 130 nm, 90 nm, 65 nm
L1 Cache	8 KB