Perhaps something like this? Maybe I need to try a BIOS update? Intel Haswell (and related architectures) processors may experience stability issues, including machine check errors (MCEs), due to a microcode bug related to REP MOVS (specifically REP MOVSB or REP MOVSQ) handling. These issues often cause system crashes or lockups, leading to microcode, BIOS/UEFI updates to resolve them. Debian Wiki +4 Issue: A high-rate of interrupts or specific memory operations can cause REP MOVS instructions to trigger Machine Check Errors (MCE) or internal errors (IERR) on older processors. Affected Processors: The bug primarily impacts older Intel processors, including Haswell and Broadwell architectures. Fix/Mitigation: The primary solution is to apply the latest motherboard BIOS/UEFI update, which contains the corrected microcode update (often labelled 20180108 or later). Background: This is linked to Intel’s efforts to fix security vulnerabilities (like Spectre), where early patches for Haswell/Broadwell caused unexpected instability, requiring further refinements. Debian Wiki +4
-Kennon > On 02/26/2026 2:30 PM PST Eliot Moss <[email protected]> wrote: > > > I know it's a low probability for a cause, but I wonder if either the > hardware or the OS have some issue with proper restartability of the > REP MOVSQ under some weird circumstance. If the hardware/firmware > does not save the in-flight register information correct (again, in > some weird and rare situation) then restarting the instruction could > fail. Might be worth: > > (a) trolling the web to see if there are reports of issues around this > instruction, Intel firmware fixes, etc. (An instruction like REP > MOVSQ is almost certainly implemented with a microcode loop, etc.) > > (b) trying this exact code with a substantially different CPU model > (which might tend to avoid any microcode bug in the model you're > using). > > Again, low probability, but ... > > Regards - EM -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
