Headless NeXTstation - accessing prom from serial

Started by Venture37, February 26, 2017, 09:08:57 am

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Venture37

I have a mono slab without a monitor or keyboard. I've build a serial lead using the following instructions & powered up the system using a 470ohm resister as per NetBSD/next68k faq

System turns out & after a moment displays on @ symbol & that's it.

Is there any way of entering the prom over serial console or forcing "port a as alternate console" without access to a monitor & keyboard?

Patching eeprom & reflashing is a possibility but I'm wondering if anything can be done otherwise (key sequence via serial?)

Venture37

I made the mistake of thinking I was dealing with flash. Long forgetting about eeprom.

I guess my two options are to reverse engineer the firmware image and modify it to enable serial console by default. binwalk & radare do not provide much info at the moment when pointed to /NeXTfiles/Software/ROM_Files/68040_Non-Turbo_Chipset/Rev_2.5_v66.BIN

Second options is to get the y-cable together which allows a mono slab to be connected to a non-adb soundbox and then set it to serial output conventionally.

Does anyone know if the rom format / layout is documented??

barcher174

Your best bet is probably to examine the previous emulator sources. The values are stored in a 32bit static RAM ( part of the rtc) which is battery backed. Perhaps you could interface to that chip to flip the bit for serial console? I see in the previous sources they already have the crc and layout figured out so you would just need to figure out a way to write to the chip in circuit.

Venture37