DOCUMENT:Q163852 TITLE :Invalid Operand with Locked CMPXCHG8B Instruction PRODUCT :Microsoft Windows NT | Microsoft Windows PROD/VER:4.00 | 95 OPER/SYS:WINDOWS KEYWORDS:kbbug kbhw kbpatch NTSrvWkst -------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation versions 4.0 - Microsoft Windows NT Server versions 4.0 - Microsoft Windows 95 -------------------------------------------------------------------------- SYMPTOMS ======== When an Intel processor receives a specific invalid instruction, your computer may stop responding (hang). Your computer must be turned off and restarted to return to normal operation. NOTE: Although there is no known operating system or application that issues such an invalid instruction, you should be aware that a program can be written maliciously to contain such an instruction. The operating system would not trap this error, as it should, which results in the processor hang. CAUSE ===== This problem can occur due to an error in the following Intel processors: - Pentium processor - Pentium processor with MMX technology - Pentium OverDrive processor - Pentium OverDrive processors with MMX technology NOTE: This problem cannot occur on the following Intel processors: - Pentium Pro processor - Pentium II processor - i486 and earlier processors This problem is known as "Invalid Operand with Locked CMPXCHG8B Instruction" and is erratum 81 on the Pentium processor errata list. For more information, please contact Intel or go to the following Intel web site: http://support.intel.com/sites/support/ RESOLUTION ========== Intel has identified a workaround to this problem that allows the operating system to trap the invalid instruction and not pass it to the processor. Microsoft has worked closely with Intel to provide the following hotfixes: Windows NT 4.0 -------------- To resolve this problem for Windows NT 4.0, obtain the following fix or wait for the next Windows NT service pack. This fix should have the following time stamp: 98/03/13 11:21p 51,968 hal.dll 98/03/13 11:21p 48,384 hal486c.dll 98/03/13 11:19p 66,496 halapic.dll 98/03/13 11:21p 46,112 halast.dll 98/03/13 11:20p 82,208 halcbus.dll 98/03/13 11:20p 80,320 halcbusm.dll 98/03/13 11:21p 46,400 halmca.dll 98/03/13 11:19p 68,640 halmps.dll 98/03/13 11:19p 67,648 halmpsm.dll 98/03/13 11:18p 79,040 halncr.dll 98/03/13 11:20p 40,192 haloli.dll 98/03/13 11:20p 56,608 halsp.dll 98/03/13 11:19p 40,768 halwyse7.dll 98/02/05 09:22p 938,816 ntkrnlmp.exe 98/02/05 09:19p 918,848 ntoskrnl.exe This hotfix has been posted to the following Internet location: ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/chp/NT40/ hotfixes-postSP3/pent-fix/ NOTE: The above link is one path; it has been wrapped for readability. Windows 95 ---------- A fix for Windows 95 is not yet available. STATUS ====== Windows NT 4.0 -------------- Intel has confirmed this to be a problem in the Intel processors listed above. A supported fix is now available from Microsoft, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information. Windows 95 ---------- Intel has confirmed this to be a problem in the Intel processors listed above. Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available. Additional query words: 95 4.00 i386 malicious hangs freeze freezes erratum cmpxchg8b compare and exchange 8 bytes cold boot hard boot ============================================================================ THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.