On Sun, Jan 6, 2019 at 12:45 AM Fritz Mueller via cctalk <cctalk@classiccmp.org> wrote:
> > • Try using the drive on the other bus if RSTS can be booted of from > > DK4. > > Easy enough experiment to try; would need to re-jumper the G740 disk > selection flip chip in the RK11-C too, I guess? No. One difference between the RK11-C and RK11-D is how it does drive selects. The RK11-C has 4 select lines on each cable, one is asserted at a time. The RK11-D has a 3 bit binary selection. There's a decoder in the RK05 (on the G740 I think) that is enabled when the drive is connected to an RK11-D. The RK03 is 1-of-4 select only which is why it works on an RK11-C and not on an RK11-D. So on the first drive connector of the RK11-C you get selects 0..3. On the second cable you get 4..7. The drive is always jumpered for 0,1,2,3. If it's jumpered as drive 0 and you connect it to the first connector it's DK0. If it's jumpered as drive 0 and you connect it to the second connector it's DK4. -tony