ah good question. It was very, very difficult to pin down. We knew our compiler was the same on both computers and compiler flags were all the same. The two

ah good question. It was very, very difficult to pin down. We knew our compiler was the same on both computers and compiler flags were all the same. The two machines were purchased at the same time and we knew everything about them was the same. We used something called a Pharlap DOS extender so our software could use beyond the 1MB boundary. It was in fiddling with that memory extender that I began to suspect a memory failure. Changing it's parameters eventually got me to fairly repeatable way to get the issue to show up not only in my app but in 3rd party software began failing too. Also, while we mostly did our work from a DOS prompt and a DOS editor (called qc) we would sometimes run Windows (Windows 3.11) which had it's own way of accessing Expanded vs. Extended memory through a DOS driver. So by swapping between the Pharlap driver and the Microsoft config.sys driver did I begin to suspect memory failure. In other words, the machine became more noticeably more unstable. I don't recall the exact name but I began running something like memcheck on the computers. Basically a memory checker and although it did not reveal the problem in its entirety, the memchecker would crash on my machine and not any of the others. These were computers running just DOS with Novell Netware network drivers for DOS/Netwware only. I reasoned that memory was failing before the memory walker/checker was getting corrupt. When I swapped main memory with another computer and the problem didn't follow the memory, my only other option was to pull out the L2 cache chips. When I put them in the computer next to mine, and finally saw the problem show up there I knew. My friend owned the computer company that sold us the computers and he later was able to test and validate my findings.