Do any tools like say Memtest86 use test patterns that will detect row hammer vulnerability and for that matter, is it something that can be fixed on any given system by changing the RAS/CAS frequency or the voltage?

Many years ago, I ran a couple of PC shops. When EDO RAM first came out we had a lot of problems with random crashes being reported by customers, usually when they were running Word. We would typically run memory tests for a few hours in QAFE, which was then the best at detecting errors, but it would consistently fail to find anything wrong with these systems.

It turned out that the most reliable way to reproduce the problem was to run the shareware version of Duke Nukem. So we had a copy of it on all our diagnostic disks. If a system could get through the first level without any on-screen corruption, you knew it wasn't going to come back to the shop, so that became a standard test on all new PCs.