DEC 3000 (alpha) faultfinding

[Maciej W. Rozycki]

On Thu, 29 Mar 2018, Peter Coghlan via cctalk wrote:

> It looks like position 0 (J8) is the normal operating position for the jumper
> then and I did not move mine previously.  With the jumper in this position,
> I get some mini console output on power up but I do not get an SROM> prompt
> and I cannot enter mini console commands unless a machine check happens or I
> force an error by removing a memory riser or doing something else to cause
> an error.

 I thought you'd get the SROM firmware to halt and wait for a command 
after POST if J8 was removed and none of the other positions shorted.  
Have you tried running with all positions open?

> (I do not get anything on the MMJ console port under any cirumstances.)

 SROM code runs from the processor's cache and it's too small for fancy 
stuff like getting through to the regular Zilog serial ports, which are 
far down on an I/O ASIC bus and require a lot of mainboard hardware to 
initialise before they can be accessed.  It's also meant to work in system 
bringup or in the presence of problems with system components, so the 
fewer pieces of logic it relies on the better.

 It's only main firmware that initialises the regular console.

  Maciej