My KDJ11-B

[Hunta]

How do you activate the mapping?

A dirty little trick As soon as the operating system writes a value to one of the UM registers, mapping is activated. In the future, I plan to use the signal /MAP

 

[bqt]

As far as I know RSX-11M Plus (starting from Version 2.1) checks if the machine has unibus mapping registers and then uses UMR for controllers that normally support only 18-bit. Even on Q-Bus machines. And a nice side effect of Version 2.1 is that when they encounter a RH controller with a Massbus Address Extension then they deactivate the UMR for RH controllers and use 22-bit addressing, so you could use a "RH70" on a Q-Bus machine (e.g. the Emulex SC03 ESDI Controller).

It depends. The RK11 driver, for example, just have the 22-bit Unibus map usage as conditional code. So it's handled or not based on your options when building the thing.
The RL11 driver on the other hand checks things dynamically.

More specifically, for the RL11, it starts by checking if the system has 22-bit addressing. If that is true, it then checks if the RLBAE register exists (which indicates it's a Qbus controller capable of full 22-bit address DMA), and if that register don't exist, it then goes for the Unibus map alternative.

 

[Hunta]

The RK11 driver, for example, just have the 22-bit Unibus map usage as conditional code.

Although not necessary...

 

[bqt]

Although not necessary...

I'm merely telling what is in the code.