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Application Note 120 Cyrix III CPU BIOS Writer's Guide Cyrix Processors Running H/F 2 REVISION HISTORY Date 11/24/99 5/20/99 4/19/99 3/22/99 3/17/99 2/23/99 1/29/99 12/14/98 9/21/98 Version 1.1 1.0 0.43 0.42 0.41 0.4 0.3 0.2 0.1 Revision Updated register 49h and DIR1 table Updated for Cyrix III Format changes, chapter 6. Changed processor internal code name from MXs to Cyrix III. Page 55: Added Core to Bus Clock Ratio Configuration Register. Added Confidential Notice. Made all pages same width. Minor changes: Changed fonts, added revision page, changed DIR table titles Cyrix III information added. Completed Table page 32 Intial First Draft based on App Notes 112 and 118. C:\documentation\joshua\appnotes\j120ap.fm (confidential) 1 Cyrix Application Note 120 - Cyrix III BIOS Writer's Guide Running H/F 2 Table of Contents 1.0 1.1 1.2 1.3 2.0 2.1 2.2 2.3 2.4 3.0 3.1 3.2 3.3 3.4 3.5 3.6 4.0 4.1 4.2 4.3 5.0 5.1 5.2 5.3 5.4 5.5 6.0 6.1 6.2 6.3 6.4 Introduction Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Cyrix Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Summary of Cyrix III, MII, 6x86MX and 6x86 Differences . . . . . . . . . . . . . . . . . . . . 4 Cyrix III CPU Detection CPU Detection and Inquiry Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 CPU Detection Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Standard and Extended CPUID Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Non CPUID Test and Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Cyrix III Configuration Register Index Assignments Accessing a Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyrix III Configuration Register Index Assignments . . . . . . . . . . . . . . . . . . . . . . . . Configuration Control Registers (CCR0-6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Address Region Registers (ARR0-7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Region Control Registers (RCR0-7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BIOS Clock Multiplier Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recommended Cyrix III Configuration Register Settings PC Memory Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 General Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Recommended Bit Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Model Specific Registers Time Stamp Counter . . . . . . . . . . . . . . . . . . . . . . . . .