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Headless NeXTstation - accessing prom from serial

 
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Venture37



Joined: 30 Dec 2005
Posts: 55

PostPosted: Sun Feb 26, 2017 2:08 am    Post subject: Headless NeXTstation - accessing prom from serial Reply with quote

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?)
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Venture37



Joined: 30 Dec 2005
Posts: 55

PostPosted: Mon Mar 20, 2017 2:41 pm    Post subject: Reply with quote

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??
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barcher174



Joined: 07 Dec 2012
Posts: 548

PostPosted: Mon Mar 20, 2017 2:48 pm    Post subject: Reply with quote

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.
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Venture37



Joined: 30 Dec 2005
Posts: 55

PostPosted: Mon Mar 20, 2017 2:54 pm    Post subject: Reply with quote

I'll take a look, thanks for the pointer Smile
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