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Cyrix CPU Detection Guide Preliminary Revision 1.01 © 1997 Cyrix Corporation. All Rights Reserved. Cyrix reserves the right to make changes in its products without notice in order to improve design or performance characteristics. The information in this publication is believed to be accurate at the time of publication, but Cyrix makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication or the information contained herein, and reserves the right to make changes at any time, without notice. Cyrix disclaims responsibility for any consequences resulting from the use of the information included in this publication. This publication neither states nor implies any representations or warranties of any kind, including but not limited to, any implied warranty of merchantability or fitness for a particular purpose. Cyrix products are not authorized for use as critical components in life support devices or systems without Cyrix's written approval. Cyrix assumes no liability whatsoever for claims associated with the sale or use (including the use of engineering samples) of Cyrix products except as provided in Cyrix's Terms and Conditions of Sale for such product. Trademarks Cyrix, the Cyrix logo, and combinations thereof are trademarks of Cyrix Corporation. 5x86, 6x86, 6x86MX, MediaGX are registered trademarks of Cyrix Corporation. MMX is a trademark of Intel Corporation. Other product names used in this publication are for identification purposes only and may be trademarks of their respective companies. Revision History REVISION 1.00 1.01 RELEASE DATE 09/30/97 10/02/97 DESCRIPTION OF CHANGES First Release (preliminary). Corrected the GXm and MediaGX values for DIR0 lookups Cyrix CPU Detection Introduction This document provides an overview of the three possible methods for detecting a Cyrix CPU. Once the correct method is identified (flowchart below), each detection method is covered in detail. This includes: How to detect the Cyrix CPU; Which CPU is present; What is the standard feature set; What are the Cyrix specific features. The three CPU detection methods are: 1. CPUID - Standard Levels This method provides the standard feature set (not vendor specific feature such as Extended MMX) and requires a look-up table. 2. CPUID - Extended Levels This is the preferred method of detection because it provides the ability to get the CPU name without requiring a look-up table. It also provides information that may be Cyrix specific. The CPUID - Extended Levels are only supported in the most recent CPUs such as GXm. 3. The 5/2 Method This method is used for older CPUs that do not support CPUID such as the 486DLC, 486SLC, 486DX, 486DX2 etc. The flowchart below should be used to determine the correct detection method. After identifying which method to use, refer to the correct section for further explanation. CPUID Supported? | No ------------------------------------------ Yes | | ( Use 5/2 Method ) Ven