[rescue] SUN2 behavior

[Romain Dolbeau]

Le dim. 6 sept. 2026 à 06:02, Dan Moisa via rescue
<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>).

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>)

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/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>).
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