<div dir="auto"><div dir="auto"><div dir="ltr">This is great, thanks for putting it together!!<div>I'm definitely not even close. Trying to take everything off the address bus since I'm seeing some weird half-level driving behavior.</div><div dir="auto"><br></div><div dir="auto">At least it's clearly not worth writing a stub boot program since diagnostic LEDs are so early in the sequence.</div><div dir="auto"><br></div><div dir="auto">Dan.</div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Sep 5, 2026 at 11:32\u202fPM Romain Dolbeau via rescue <<a href="mailto:rescue@sunhelp.org" rel="noreferrer noreferrer" target="_blank">rescue@sunhelp.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Le dim. 6 sept. 2026 à 06:02, Dan Moisa via rescue<br>
<<a href="mailto:rescue@sunhelp.org" rel="noreferrer noreferrer" target="_blank">rescue@sunhelp.org</a>> a écrit :<br>
> 1. What LED diagnostic sequence do you get, if any, if you run the board just by itself - no RAM, nothing else on multibus,<br>
<br>
Out of a cold reset. The CPU first fetches two words, the initial SP<br>
and PC (<<a href="https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/romvec.s#L15-L16" rel="noreferrer noreferrer noreferrer" target="_blank">https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/romvec.s#L15-L16</a>>).<br>
<br>
It will then jump to the address stored in the SP<br>
(<<a href="https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/trap.s#L71" rel="noreferrer noreferrer noreferrer" target="_blank">https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/trap.s#L71</a>>)<br>
<br>
At that point it sets a few systems registers and then set the LEds to<br>
L_INITIAL (<<a href="https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/trap.s#L109" rel="noreferrer noreferrer noreferrer" target="_blank">https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/kernel/trap.s#L109</a>><br>
, <<a href="https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/h/s2led.h#L22" rel="noreferrer noreferrer noreferrer" target="_blank">https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/h/s2led.h#L22</a>>).<br>
That is the first deliberate change to the Leds.<br>
<br>
After more system setup, it jumps to PowerUpReset that immediately go<br>
to _qpdiag (<<a href="https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/diag/diag.s#L35" rel="noreferrer noreferrer noreferrer" target="_blank">https://github.com/calmsacibis995/sunos-34-src/blob/7fcdbbecbbde0ccf28a923c533a5f20ed90d9ccb/sun/prom_monitor/rsun/mon/diag/diag.s#L35</a>>).<br>
The first thing _qpdiag will do is the "marching one" so the user can<br>
check all the Leds are working.<br>
<br>
After that, it goes for hardware testing starting with the MMU, and the Leds do:<br>
<br>
=> L_SM_CONST<br>
=> L_SM_DATA<br>
=> L_SM_ADDR<br>
=> L_PM_CONST<br>
=> L_PM_DATA<br>
=> L_PM_ADDR<br>
=> L_PROM<br>
=> L_M_MAP<br>
=> L_SETUP_MEM [that one fails without memory]<br>
=> L_SETUP_MAP<br>
=> L_SETUP_FB<br>
=> L_SETUP_KEYB<br>
=> L_RUNNING<br>
=> L_HEARTBEAT<br>
=> L_RUNNING<br>
=> L_HEARTBEAT<br>
(repeat the blink)<br>
<br>
So if you never reach the Leds as 0x1 (L_INITIAL), the CPU can't even<br>
fetch the initial words or can't set the Leds at all.<br>
If you see the "marching one", CPU is good, and so is the /DTACK logic.<br>
After that, you need the Led pattern to tell where things went wrong.<br>
<br>
Cordially,<br>
<br>
-- <br>
Romain Dolbeau<br>
<br>
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</blockquote></div></div>