5500 board won't POST/chime w/o the Display hooked up?

[Trash80toHP_Mini]

I've got a test rig that'll boot Alchemy and Gazelle boards, but not my AIO 5500 sub-variant of Gazelle. Does it fail to POST due to lack of internal CRT hookup or might there be another issue with this particular board?

If display is indeed the problem, will it POST with the external display/projector cable in lieu of the A/B CRT hookup?

 

[joevt]

Is the 6500/TAM emulation of DingusPPC good enough to test this? It might be missing some stuff that makes the emulated machine identify itself as a 5500 AIO if such stuff exists.

Would need to compare dump-device-tree and DumpNameRegistry and System Profiler and UnivTables low memory globals.
https://68kmla.org/bb/threads/skipping-the-startup-memory-test.50699/post-570896
https://forums.macrumors.com/thread...l-work-in-a-beige-power-macintosh-g3.2303689/
https://68kmla.org/bb/threads/how-does-the-l2-cache-work-on-nubus-powerpc.47395/post-572444

 

[Trash80toHP_Mini]

Hi, Joevt, hoped you'd join in here. Just rebuilt the TestBed and have successfully tested 6360/6400 boards but haven't located my 6500 board. I'd though I might have corrupted my CF boot disk, but it was the reader that died?

My first thought was that there might be some machine ID setup on the board to blame for this like the 475/605 twiddler? That's the only way I can think of offhand to make the 5500/6500 fork in the road before POST hits ROM?

Looking for my 6500 board to backcheck the situation.

 

[joevt]

The OHare ID register might have some Machine ID info.
Use probe-ids in Open Firmware to probe it.
https://68kmla.org/bb/threads/photo-request-5500-6500-and-tam-logic-board.46450/post-576941

 

[Trash80toHP_Mini]

Won't the board need to at least power up to play with whatever you call communicating at low level over a serial connection? Dug my 6500 board out of the Classic it's been sitting on its head in for two decades. It powers up/chimes, but no video out for some reason. I'll dig out the proper two story Video Out/Sub driver variant and see if that makes a difference, doubtful, but another base to cover.

 

[joevt]

Won't the board need to at least power up to play with whatever you call communicating at low level over a serial connection?

Yes. You are able to do that by connecting a display?

Get into Open Firmware, do the probe-ids. Disconnect the display while still in Open Firmware. do probe-ids again. We'll see if there's a connection between the ID's and the display connection.

What does failure to post look like? no startup chime? I wonder if it enters the Serial Test Manager?