id summary reporter owner description type status component version resolution keywords cc guest host 16375 Ubuntu 16.04 LiveCD Guru Meditation on Win-64 host, works on the same Win-32 host (Intel Pentium D) Socratis "* '''Host''': Pentium-D based, triple-booting Win7-32/Win7-64/Win10-64. * '''Guest''': Ubuntu 16.04-64 LiveCD. * '''vbox''': Default 5.1.12 template for Ubuntu-64, with 64MB vRAM assigned. * '''!VirtualBox''': 5.1.12 While starting the VM on the Win7-32 host works fine, starting the exact same VM on the Win7-64 or Win10-64 version on the same host, causes a Guru Meditation: {{{ VCPU0: Guru Meditation 1155 (VINF_EM_TRIPLE_FAULT) }}} The issue was brought to my attention by another user (mycroft1) in the thread [https://forums.virtualbox.org/viewtopic.php?f=3&t=81353 Meditation Guru critical error on Windows Host], and since I had an almost identical system, I gave it a try with the above mentioned results. The system is a rather old one with an Intel Pentium D @ 3.2 GHz with 2 physical / 2 logical CPUs. From the logs, one of the very few differences between the 32- and the 64-bit of Win7 (and Win10-64), is that at the 32-bit version log, there are the following extra lines: {{{ 00:00:03.238127 [/REM/] (level 1) 00:00:03.238129 64bitEnabled = 0x0000000000000001 (1) ... 00:00:03.318995 REM: VBoxREM64 00:00:03.319101 Using 64-bit aware REM }}} and there's a difference between them: {{{ 00:00:03.243747 PGM: Host paging mode: PAE+PGE : Win7-32 00:00:05.044710 PGM: Host paging mode: AMD64+PGE+NX : Win7-64/Win10-64 }}} Logs and other information are already [https://forums.virtualbox.org/viewtopic.php?f=3&t=81353 available on the thread], they can be duplicated here if you want, just say the word." defect closed VMM VirtualBox 5.1.12 fixed Linux Windows