@gabrielesvelto In the old days MS-DOS used to do a quick memory check when loading himem.sys. This used to annoy me because on systems with more than 4MB of RAM, this can take a while. So there's an option to disable it, and in the DOS manual where this setting is, they explain that they had to enable it by default because the very large amount of memory out there is flaky, and lots of issues are caused by it. It seems that not much has improved, ECC should become default these days.