Michael J. Mahon wrote:
Is it manufactured or added by someone? It was popular to install a switch to disable the "zapping" of the RAM card by the DOS 3.3 card loader, so that changes could persist across re-boots. (Another more persistent way to do this mod was to lift an IC pin.)
It's manufactured. You're likely right on that
It's a shame that Apple didn't use keyed connectors for the disk cables--it would have save a lot of grief. On the controller, they used the right-angle header so that putting the connector on wrong way requires deforming the header and squeezing the cable against the card--sort of a makeshift "key", but not nearly as good as the real thing. And, of course, there's nothing to help on the analog card end.
A few third party disk controllers had keyed connectors. Of course a lot of drive cable weren't keyed. Still a keyed connector on the card kept you from being one pin off. Wayne