Embedded devices did not necessarily use the c++ memory model, and definitely not in the 90s and were highly likely in order CPUs to boot with no crazy compilers and thus atomics didn’t matter too much anyway (volatile was sufficient). They had a weaker memory model maybe but at the same time multi threading on embedded did not really exist as it was only being introduced into the industry with any real seriousness around that time (threading on Linux started to shake out around the mid 90s).