PDP-11/45 RSTS/E boot problem

[Tony Duell]

On Sun, Jan 6, 2019 at 12:45 AM Fritz Mueller via cctalk
<cctalk at 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