IBM CORE MEMORY TEST ROUTINES
IBM provides two routines to test memory, called the high and low test. The only difference is where they place the executing code because those locations aren't checked. Each of these will also check the wraparound capability. The highest address on this machine is 8191 decimal or 1FFF in hex. If you add to the address it should wrap around to 0, which the tests verify.
The tests have six stages. The first will write all 1 bits in each location and then all 0 bits. The second writes the address of a word into that location, so that the addressing logic can be verified. The third writes alternating AAAA and 5555 patterns, called a checkerboard. The fourth first sets all bits 0 except for moving a 1 from left to right in the word, then it does the complement with all 1 and a moving 0. The fifth and sixth will write alternating blocks of ones and zeroes which is the worst case pattern for generating noise that can trigger a misadjusted sense amplifier.
SETTING UP THE TEST CODE
I used the IBM 1130 Simulator to boot the 1442 Relocating Loader with the Hi Memory diagnostic behind it. When it stopped at the first wait, I dumped the memory to a file that I can use to load core in the physical 1130. I then did the same but with the Lo Memory diagnostic, giving me a second load file.
My Memory Load Tool will toggle these into core after which I can set the IAR to the address of the wait and push Prog Start to run the tests. I need as much information as I can get to hunt down the problem this machine is having with the bit flip and parity stop.