"I do not know if the silly (because you have no idea what it does, and it can not do what you need) IDE does re oh51, but if that is not automatically run, then you are looking at a binary file."

I think that is the key to my questions. Since the start of time our company has been taking the binary file produced by the old assembler and using it to program the mcu. We only use the hex file with the CEIBO emulator.

I wanted to compare apples to apples so I tried comparing the old binary file to the Absolute Object File. The ABS has additional info at the beginning of the file. Once I converted it to hex as Erik suggested, the code in the file disassembles just fine. I'll make sure we use the hex files produced by Keil to program the mcus in the production line.

Thanks much!

Marek