[Simh] something strange with simulated RK05 drive ?

[Johnny Billquist]

And I need to slightly correct myself, now that I've read through the 
RK11 documentation...

On 2020-02-12 02:02, Johnny Billquist wrote:

> But I did now... And I don't agree with you. simh is setting an error 
> state if you ask for a too high cylinder. And the error is exactly what 
> Henk described. RKER_NXC is set.
> 
> You are misunderstanding what Henk wrote.
> 
> However, with that said, Henk have misunderstood the system. It is 
> important to understand that the disk drive and the controller are two 
> separate entities. The fault light is only about error conditions on the 
> disk drive, not the controller.
> Out of cylinder errors are caught by the controller and never even gets 
> to the disk drive, so there is nothing that the disk drive will indicate 
> for this.
> 
> Henk, you need to understand how these systems work a little better. :-)

To be very clear. The RK11 Error register have pretty much nothing to do 
with the error indicator on the RK05 disk drive. You can possibly make 
some educated guess from the drive status register, but the Error 
register is basically about the RK11, and not the RK05.

However, the cylinder error is not absolutely local to the controller, 
as I assumed. In fact, the RK11 sends the cylinder over to the drive, 
and the drive responds either with an Address Error, or Address 
acknowledge signal to this. That in turn drives the cylinder error bit 
in the controller.
But the disk drive itself does not drive any error indication based on this.
Drive errors are about internal things of the disk drive. simh actually 
do not at all simulate this side, so you are in fact entirely on your 
own here. There is nothing really in simh for you.
simh is emulating things up to the point of the registers and interrupts 
of the controller, but beyond that it does not at all reflect how the 
real system works.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol