RK11-D "diskless" test ZRKJE0???

Fritz Mueller fritzm at fritzm.org
Thu Jul 9 19:20:54 CDT 2020

> On Jul 9, 2020, at 5:02 PM, Robert Armstrong via cctech <cctech at classiccmp.org> wrote:
> I have an 11/04 with an RK11-D.  I have a couple of RK05s, but I wanted to test the controller before I start working on the drives.  The PDP11 Diagnostic Handbook says that ZRKJ?? "checks only the drive-independent logic of the RK11 controller. no drive is needed..."  I assumed that meant it was a diskless test, but now I'm not sure that's true.  Can anyone confirm or deny this?

Hi Robert,

My experience with an RK11-C on a PDP-11/45 is that the drive-independent diagnostic does in fact work with no drives attached. For the RK11-C at least, it does clever things with maintenance-mode to simulate signaling that would source from the drive where necessary.

I know there are some differences between the RK11-C and the RK11-D -- if some of these are related to maintenance mode, it could also be that you need to verify that the version of the diagnostic you are running is RK11-D (and not just RK11-C) aware?

Another possibility is that you should pull the BC11 and add another terminator rather than leaving it dangling?


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