Using two RL02 drives on OS/8?

At 01:27 AM 2/9/2013, Charles wrote: That's what I was worried about. You're lucky that it hasn't scrambled the OS on your drives. :) Yup. The original for this (from the RL01/02 pocket service guide) didn't have anything to do a drive select so I added it in. That shifted everything, leading to all the offsets shifting. I missed fixing the comment there, but jmp to 0204 is correct. -Rick I'm pulling my hair out... I disconnected the 2nd drive and now just have one RL02 attached to my RL8A, with a terminator. A bit of background - I could not find a cable that goes from the 40 pin header on the controller card to the first drive, so I made one out of ribbon cable and IDC headers, removing the first external connector and just using headers as it does inside the drive. Now I'm beginning to wonder if the original cable has a "twist" somewhere in the drive selects like the old PC floppy cables, because... Although I can set and reset the two drive select bits on the RL8A, and the 75113 line drivers also change state appropriately, those signals are not reaching the correct place on the logic board inside the RL02! At the 75107 line receivers (E57), those two bits are always logic 00, i.e. drive 0. So the drive won't select at all unless I put the Unit 0 plug in, at which point it effectively ignores the drive select bits and always selects regardless of the state of those two bits at the controller. Confirming that the drive select lines are dead. The only thing between the line drivers and receivers is 6' of ribbon cable. It leaves the RL8A on J1 header pins TT, SS, RR, PP and is supposed to enter the RL02 logic board on J12 header pins C, D, E, F which accounts for the cable being reversed. Just in case I even tried flipping the header connector around and of course the drive won't load or work at all and the Fault light stays on, so I know I have it facing the right way. Unless it's possible to make a cable upside down and backwards, or some such? This setup DID previously run OS/8, ADVENT, FOCAL, whatever was on the pack, but only using one of the RL02's (I don't think I was ever able to access the other drive). I can't think of anything that could "lose" the drive select lines except a defective cable (will continuity-check tomorrow, even though I made a new one by copying the old one that used to work) or else the correct cable (BC80J-20) is not a straight-through pin for pin connection, in which case I have to have one. Just to further confuse things, I have the identical two-drive setup with homemade controller-to-drive cable on my 11/23+ and RLV11 card, and it works perfectly. So now I'm just going in circles... that's enough for tonight! EDIT: Additional note: When the two-drive system was running OS/8, I had the ribbon cable going to the bottom drive in the rack which had Unit 1 plug, then the proper BC20J cable from there to the top drive with Unit 0 plug. Makes me wonder anew if there is something non- obvious about the connections of the drive select lines within the DEC cables...