7600 Can't get into OpenFirmware

[dankcomputing]

I get a black screen of nothing if I try. The system boots and runs normally (well, I am chasing another problem with getting USB cards working but I don't know if this is connected). I have mashed the CUDA button plenty of times, reset PRAM, PRAM battery is working. The machine apparently shipped as a 7600/133 but there's a Power Computig 150mhz CPU card in the CPU slot. I have no idea if it was an upgrade or pinched from a Power Computing clone, and I have no other CPU cards to test.

 

[LaPorta]

I thought OF only became a thing with new world ROMs/ OS X?

 

[dankcomputing]

This is apparently one of the first systems to have it. Is it possible that it only works over TTY?

 

[finkmac]

all pci powermacs have open firmware
iirc most (all?) old world pci powermacs will default to serial output for the open firmware prompt

 

[dankcomputing]

OK that makes sense. I'm just wondering if something in there's been messed with as I can't get any of the 4 USB cards I have on hand to work no matter what drivers I install. The CPU also still shows as 133 mhz in System Profiler even though it should be 150.

Are OpenFirmware settings saved in a flash chip separate from the PRAM or does it reset to defaults when the PRAM is reset?

 

[aladds]

Pretty sure XPostFacto has an option to set the OF console to internal video/keyboard from OS 9.

 

[Phipli]

Pretty sure XPostFacto has an option to set the OF console to internal video/keyboard from OS 9.

This - XPostFacto let's you change OpenFirmware from the default modem port to keyboard and monitor...

But it is a little buggy - often hangs if you type too quickly or do something as wild as... Pressing delete. It didn't really start playing ball from keyboard input until the New World era.

 

[LaPorta]

Why in the world would they want it through the serial port to start?

 

[Phipli]

Why in the world would they want it through the serial port to start?

Because then they can copy and paste from another machine to debug a machine they're bringing up?

 

[dankcomputing]

It does make it much less likely that someone's messed with the configuration. If it was messed with and not reset, I probably would be getting a local console and not the default serial console.

It does appear that there's no extra EEPROM or whatever storing the OpenFirmware settings and that it's just using PRAM. Maybe it's different on later systems?

 

[joevt]

On New World Macs, NVRAM is stored on the same flash chip as the ROM. The ROM is a flash chip and therefore can be modified.

On Old World and New World Macs, NVRAM is 8KiB and there's a section reserved for PRAM settings and a section reserved for NVRAM settings and a section reserved for non volatile device properties (such as display preferences for a GPU) and some other sections. Old World and New World have different formats for the NVRAM settings and non-volatile device properties sections.

In Mac OS 9, My DumpDisplayRegistry app can dump the NVRAM and it indicates the non-volatile device properties. https://68kmla.org/bb/index.php?threads/skipping-the-startup-memory-test.50699/post-570896

Note: Open Firmware is two words.