>From memory, when I looked into doing this I found that the RQDX3 BA23 >distribution panel maps DS2 from the contriller to all DS pins on the B cable >of one drive and DS3 to all DS lines on the other. I never did test the theory >though. I did not get a special adapter from decromancer. Hope it helps Nigel
On August 12, 2023 6:35:35 p.m. EDT, Peter Coghlan via cctalk <[email protected]> wrote: >> >> I have a Gesswein MFM emulator from decromancer.ca; who offer an adaptor >> that yields a 2nd MFM data connector. >> I'll use mine in a Microvax 2000. Does anyone know how to hook it up as >> two MFM drives in a Microvax 2000? >> >> The vendor sold a 1in high adaptor box, BA40A, with DD50 connectors to a >> second cabinet (same as CPU box) for a second drive. >> DEC configured both primary and secondary drives identically (drive 3, IIRC). >> The Microvax 2000 Technical Manual gives the pinout from the mother board >> to the MFM/floppy daughterboard, but I can't find the pinout from that >> daughterboard to the cables anywhere. >> >> I've been looking for a BA40A, for some years now, to trace the pin layout >> for a 2nd drive. Does anyone know it? >> Has anyone successfully configured a single MFM emulator as two MFM drives >> in a Microvax 2000? Or to an RQDX3? >> > >I've had two real MFM drives running with one of my VAXstation/MicroVAX 2000 >machines but it is a long time since I've looked at this stuff so I'm not >certain of the details. > >I didn't use any adapter box or cables with DD connectors. I only had the >original DEC ribbon cable that connects from the VAX motherboard to one MFM >drive and one RX33 floppy drive. I used this as a guide to make up a new >longer cable with an extra 34 pin edge connector in parallel with the first >MFM drive control connector. I ran this cable out through the hole in the >bottom of the case where the cable to the adapter box was intended to run >so that the added connector could be placed on an external MFM drive. >I also connected a straight through 20 pin IDC to edge connector ribbon cable >salvaged from a PC from the vacant 20 pin IDC connector on the VAX motherboard >to the data connector on the second MFM drive, running it out through the >same hole in the VAX case. > >IIRC I had to jumper the second MFM drive as drive 4. Presumably I should >have made a twist in the cable to allow the second MFM drive to be configured >as drive 3, the same as the first drive. > >I think the first MFM drive showed up as DUA0, the second one as DUA1 and the >floppy as DUA2. > >I recall an incident when I tried to connect one particular second MFM drive >externally and the VAX refused to power up. It seemed the overcurrent trip >was operating in the power supply and the extra drive appeared to be the >cause of this. I'm a bit hazy on exactly what I did to try to get around >this issue, I suspect I tried powering up the VAX with the drive disconnected >and connecting it after power up. Anyway, the upshot was that one or two of >the conductors in the 20 pin data cable got extremely hot and the insulation >on them started to smoke before I quickly switched off. I'm not sure but I >think the reason was that the particular drive placed an unfused +5V on some >pins on the data connector and the corresponding pins were grounded at the >VAX end. Or it could be the other way around... Luckily there was no damage >to anything other than the cable. > >Regards, >Peter Coghlan.
