[rescue] SUN2 behavior

[Dave McGuire]

   That sounds a lot like bus contention; I wonder if another driver is 
errneously enabled, driving at the opposite state.

             -Dave

On 9/6/26 15:20, Dan Moisa via rescue wrote:
> This is great, thanks for putting it together!!
> I'm definitely not even close. Trying to take everything off the address 
> bus since I'm seeing some weird half-level driving behavior.
> 
> At least it's clearly not worth writing a stub boot program since 
> diagnostic LEDs are so early in the sequence.
> 
> Dan.
> 
> On Sat, Sep 5, 2026 at 11:32 PM Romain Dolbeau via rescue 
> <rescue at sunhelp.org <mailto:rescue at sunhelp.org>> wrote:
> 
>     Le dim. 6 sept. 2026 à 06:02, Dan Moisa via rescue
>     <rescue at sunhelp.org <mailto:rescue at sunhelp.org>> a écrit :
>      > 1. What LED diagnostic sequence do you get, if any, if you run
>     the board just by itself - no RAM, nothing else on multibus,
> 
>     Out of a cold reset. The CPU first fetches two words, the initial SP
>     and PC (<https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/kernel/romvec.s#L15-L16 <https://github.com/calmsacibis995/
>     sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/
>     prom_monitor/rsun/mon/kernel/romvec.s#L15-L16>>).
> 
>     It will then jump to the address stored in the SP
>     (<https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/kernel/trap.s#L71 <https://github.com/calmsacibis995/sunos-34-
>     src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/
>     rsun/mon/kernel/trap.s#L71>>)
> 
>     At that point it sets a few systems registers and then set the LEds to
>     L_INITIAL (<https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/kernel/trap.s#L109 <https://github.com/calmsacibis995/sunos-34-
>     src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/
>     rsun/mon/kernel/trap.s#L109>>
>     ,  <https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/h/s2led.h#L22 <https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/h/s2led.h#L22>>).
>     That is the first deliberate change to the Leds.
> 
>     After more system setup, it jumps to PowerUpReset that immediately go
>     to _qpdiag (<https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/diag/diag.s#L35 <https://github.com/calmsacibis995/sunos-34-src/
>     blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/
>     mon/diag/diag.s#L35>>).
>     The first thing _qpdiag will do is the "marching one" so the user can
>     check all the Leds are working.
> 
>     After that, it goes for hardware testing starting with the MMU, and
>     the Leds do:
> 
>       => L_SM_CONST
>       => L_SM_DATA
>       => L_SM_ADDR
>       => L_PM_CONST
>       => L_PM_DATA
>       => L_PM_ADDR
>       => L_PROM
>       => L_M_MAP
>       => L_SETUP_MEM [that one fails without memory]
>       => L_SETUP_MAP
>       => L_SETUP_FB
>       => L_SETUP_KEYB
>       => L_RUNNING
>       => L_HEARTBEAT
>       => L_RUNNING
>       => L_HEARTBEAT
>     (repeat the blink)
> 
>     So if you never reach the Leds as 0x1 (L_INITIAL), the CPU can't even
>     fetch the initial words or can't set the Leds at all.
>     If you see the "marching one", CPU is good, and so is the /DTACK logic.
>     After that, you need the Led pattern to tell where things went wrong.
> 
>     Cordially,
> 
>     -- 
>     Romain Dolbeau
> 
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> 
> 
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-- 
Dave McGuire, AK4HZ
New Kensington, PA