Hi. I've only recently joined this forum after I became a D8B owner a few weeks ago. This being my first post, I hope I'm doing it correctly. In keeping with most people on this forum I'm having my share of faults, problems and teething troubles with the D8B although I'm a great admirer of it. But to stick with the topic, re the question of the location of the ENS on the Brain Board I thought I'd contribute my 2 cents worth. I can say that it is not resident in the eprom (U38 on the schematic). To test this I made a copy of the eprom and installed it on another Brain Board (I managed to get a range of spares with the mixer). The system worked with this arrangement but the ENS reported was that of the substitute board. Naturally OS 5.1 authorisation was being sought. If one looks at the relevant schematics and the pdf called "chipper2" (a list of all the chips used throughout the D8B) you'll see reference to U16 (a DS2401) which is a so-called Silicon Serial Number.
http://pdfserv.maximintegrated.com/en/ds/DS2401.pdf
for more info. It connects to U25, the large DSP chip. I'm at a loss as to what can be done with this knowledge, except perhaps to transfer the chip to another Brain Board should the original go faulty - desoldering/soldering skills permitting!
Terry.