Memtest86 gives a false sense of security.

[streetwolf]

Here's the deal. I can run Memtest86 for hours on end with no errors at all. However, when I go into Windows 10 I have situations where memory errors cause me problems. This is particularly evident when I create disk images using StorageCraft's SPX program. While the backups will show as successfully created, verification will fail. This is a simple MD5 hash. If I loosen memory timings or reduce the frequency, verification runs successfully. Luckily, I always check my image log to see if verification was successful. If an image doesn't verify I can't use that image to restore my drive in case of emergency in SPX's PE environment, the restore fails. Another program that is evidently memory sensitive is Firefox. I suffer tab crashes when I o/c memory a little too much. So what good is Memtest86 when the main reason to run it is to have a stable OS as far as memory is concerned?

Will you agree that memory passing in Memtest86 does not mean memory problems won't happen in the OS? Your comments on this issue will be appreciated.

[David (PassMark)]

Some possibilities for MemTest86 missing errors,

1. You aren't using MemTest86 in an optimal fashion. In particular, are you using the latest release and are you using multithreading? The single threaded test isn't nearly as effective and using all CPU cores. The paid for version also has a couple of additional tests.
2. The system instabilities aren't due to bad RAM at all, but something else.
3. The RAM is running on the edge of failure (due to pushing the timings to the limit & overlocking) but only becomes unstable in combination with some external factors. For example the slight increase in temperatures or increase in EMI from having the entire system under load might push the RAM over the edge into a failure case. i.e. you have no safety margin. This is where BurnInTest can help by fully loading the system while testing RAM.
4. You got unlucky, and the weak RAM cells happen to be at addresses that are reserved by the system. UEFI BIOS reserves some RAM for the firmware and UEFI data. This RAM can not be tested (generally it is only maybe 2% of all the RAM, but sometimes you get unlucky). A example of this memory map can be seen here.