Service Manuals, User Guides, Schematic Diagrams or docs for : . Rare and Ancient Equipment VIA VIA Cyrix III Thermal Specifications
<< Back | HomeMost service manuals and schematics are PDF files, so You will need Adobre Acrobat Reader to view : Acrobat Download Some of the files are DjVu format. Readers and resources available here : DjVu Resources
For the compressed files, most common are zip and rar. Please, extract files with Your favorite compression software ( WinZip, WinRAR ... ) before viewing. If a document has multiple parts, You should download all, before extracting.
Good luck. Repair on Your own risk. Make sure You know what You are doing.
Image preview - the first page of the document
>> Download VIA Cyrix III Thermal Specifications documenatation <<
Text preview - extract from the document
Application Note 126
Cyrix III CPU
Thermal Design Considerations
REVISION HISTORY
Date Version Revision
5/20/99 1.0 Updated Cyrix III Information
3/22/99 0.21 Changed name from MXs to Cyrix III processor.
3/1/99 0.2 Changed case temperature from 70 to 85 degrees.
1/29/1999 0.1 Initial Version C:\documentation\joshua\appnotes\cIII_thermal.fm
Based on App Note 103
APPLICATION NOTE 126 Cyrix III Thermal Design
Considerations
Introduction
This Application Report serves as a guide in the thermal design of a personal computer
using the Via Cyrix III CPUTM Microprocessor. A simplified thermal model is presented
that utilizes thermal resistances to describe the heat flow from the CPU. Two case stud-
ies are included to show how to measure the thermal performance of the microprocessor
in a typical computer enclosure. Additional examples illustrate the calculation of
expected maximum case and ambient temperatures. The D.C. Specifications and ther-
mal data in the Cyrix III Microprocessor Data Book (when available) are expanded and
updated by the Appendix in this Application Report.
3 Cyrix Application Note 126 - Cyrix III Thermal Design Considerations
Heat Flow
Heat Flow
The Cyrix III CPU dissipates as much as 11.4 watts of power depending on the
CPU clock frequency. The CPU is mounted up-side-down in a PGA package (Fig-
ure 1). Most of the heat is concentrated at the surface of the semiconductor chip and
is passed to the package through three main paths: (1) through the bulk of the sili-
con chip to where the chip is mounted to the package, (2) through the bond wires to
the package, (3) through radiation across the void between the chip and the bottom
of the package.
The package is cooled by radiation, convection and conduction. Some heat is con-
ducted through the pins and the socket, but most of the heat passes from the pack-
age into the flowing air stream that carries the heat out of the equipment enclosure.
The transfer of heat from the package to the ambient air can be greatly enhanced
through the use of a heatsink. Our thermal model will concentrate on the heat flow
from the case and heatsink to the surrounding air.
COPPER / TUNGSTEN
HEAT SPREADER SILICON CHIP
CERAMIC
BOND
WIRES
NOT TO SCALE
Cyrix III CPU PGA Package Cross-Sectional View
4 Cyrix Application Note 126 - Cyrix III Thermal Design Considerations
Thermal Resistance Model
Thermal Resistance Model
As heat flows from a heat source to a cooler object, there is a temperature drop
(T0 -T1) which is similar to the voltage drop (E) across an electrical resistor.
Electrical power dissipated in the chip (P) generates heat. The heat flows away
from the source analogous to electrical current (I). By dividing the temperature
drop
(T0 - T1) by the power producing the heat (P), we obtain thermal resistance ()
expressed in Celsius degrees (◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo