Transmeta Crusoe undocumented features

Last Update:
2000-09-29

Introduction

Since its release in early 2000, Transmeta Crusoe remains the most mysterious x86 CPU. It's the only contemporary CPU for which the common documents are not available to an average human being. I registered to receive the Crusoe documents as soon as they opened their website, and I still didn't get ANY answer from them. So I started searching for information on Crusoe that could be more precise than the general desciption available everywhere.
Here are some results of my hunting:

CPUID on Transmeta Crusoe

Transmeta crusoe supports standard CPUID, AMD-style extended CPUID and its very own extended CPUID (somehow I believe that the last one can be attributed to Christian). Of these, the Transmeta extended CPUID is of course the most interesting one. Here it is:

EAX=0x80860000

Return the maximim Transmeta CPUID level in EAX.

EAX=0x80860001

CPU detailed revision, (nominal?) operating frequency and Transmeta features(operating mode?).
EBX = CPU revision
ECX = nominal frequency
EDX = features:

bit 0 - LongRun power management supported
bit 1 - ???

EAX=0x80860002

Code Morphing Software revision
EBX:ECX - software revision

EAX=0x80860003..0x80860006

CPU name string.
The CPU name string is 64 bytes long. It starts with LSB of EAX returned by CPUID 0x80860003 and ends with the MSB of EDX returned by CPUID 0x80860006.

EAX=0x80860007

Current CPU operation information.
EAX = core frequency
EBX = core voltage
ECX = performance percentage

Crusoe MSRs

MSR 0x80860010

(based on Transmeta presentation at Hot Chips 12, extracted by Christian Ludloff)
bits 63..32 = max. performance percentage
bits 31..0 = min. performance percentage