Ytdyklly

When starting Memtest86+ version 5.01, there is a blinking message:

==> Press F1 to enter Fail-Safe Mode <==

If I hit F1 there is the usual progression screen, except that the RAM information (freq, timings ...) is replaced by the message:

**** FAIL SAFE **** **** FAIL SAFE ****

No Detection, same reliability

So I understand that memory errors are not detected and that the computer is only stress-tested (which could be useful to test if CPU is good when we now that the RAM is faulty). Am I right ? There is little information about this on the website.

According to the source code:

        /* F1 */

        if(c == scs) { v->fail_safe |= 1;       break; }

Pressing F1 sets the fail_safe 1 bit (same variable is used for other things as well), and then...

/* Find Memory Specs */

if(v->fail_safe & 1)

        {

                cprint(LINE_CPU, COL_SPEC, " **** FAIL SAFE **** FAIL SAFE **** ");

                cprint(LINE_RAM, COL_SPEC, "   No detection, same reliability   ");

        } else {

                find_controller();

                get_spd_spec();

                if(num_cpus <= 16 && !(v->fail_safe & 4)) { coretemp(); }

        }

...it skips the "find memory specs" step. Basically this detects what type of memory you have (DDR3, DDR4, ECC, clock speed, etc.) which memtest86+ usually displays on the right hand side.

Why is it called failsafe? My guess it's because memtest86+ operates on a very low level and a single wrong step would cause it to crash entirely. So maybe doing this detection step crashes some systems, and by pressing F1 maybe you can get past that crash and still use the program.

I have also found some old posts in the Memtest86 forums asking about failsafe but zero answers.

http://forum.canardpc.com/threads/83104-Memtest86-5-01-(finally)-released?p=7066673

Tips : F1 will enable fail-safe mode, F2 will enable SMP Mode (disabled by default) and F3 will trigger an hidden alternative SMP Mode.

(From reading the source code, those are mutually exclusive, you can only pick one of them or wait for input timeout to commence regular operation.)

As long as the program works for you, I guess there is no need to worry about it.