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Comment by accrual | Hacker News Reader

I am a big fan of 86box for my retro PC hobby. Some neat things I've used it for:

* Log virtual POST codes to a text file for a physical motherboard I'm troubleshooting to see where it's hanging up

* Install an old OS to a .img file which I can then extract and pull bit-perfect files from

* Create a virtual hard drive with matching CHS values to a real hard drive, install an OS, then write the image to a real disk and boot it on real hardware

* And of course, play around with old hardware, software, and games in fairly accurate simulated way :)

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>Log virtual POST codes to a text file for a physical motherboard I'm troubleshooting to see where it's hanging up

I went as far as simulating defects by modifying individual hardware blocks in 86Box source code, recompiling, and checking resulting POST code because that seemed faster than carefully tracing BIOS :)

"Modified 86Box to break RTC always returning 0 or 0xff. POST_7 freeze." https://www.vogons.org/viewtopic.php?p=1041079#p1041079

That's awesome, rasz! It's amazing how 86box allows us to peer into hardware we otherwise couldn't easily access. 8)

I was blown away how easy and fast whole process was. I posted about my plan at 14:33 and results at 16:55. I even commented at the time how "setting up build env and compiling 86Box was a breeze".

> Log virtual POST codes to a text file for a physical motherboard I'm troubleshooting to see where it's hanging up

That sounds awesome but my brain can't follow today.

What did the setup look like here?

My brain's looking at a test motherboard, then at 86Box (which would presumably run on your main system), and I can't figure out how to connect the dots.

Definitely! I've been meaning to write a post about it.

I had a 486 motherboard that would hang somewhere during POST. I have a POST card that displays the current code from the ISA bus, but even with my phone camera in slow-mo mode, I wasn't able to capture the full list of codes - the value on the bus changed faster than what the POST card could output.

I turned to 86Box and found a very similar 486 board with the same chipset. There's an option to install a virtual POST card and show the codes in the application's status bar, but this also went by too fast for me to see what was going on.

So I downloaded the source, found the file for the POST card, and edited it to write the codes to the console as well. Then I fired up the virtual board again and produced a complete log of the POST codes during a cold start.

Together with the complete list from 86Box plus the codes from the real board, I found it was completing many steps but hanging on "chipset initialization". I still have some work to fix it, but it at least gave me some insight I wouldn't have otherwise had. :)

That is crazy and awesome that the virtual POST card (brandnewsentence) modeled the real environment so closely. Feels obvious that it would line up - once proven, haha.

I would have been yelling at an Arduino (and possibly a shift register) wired to the 7-segment LEDs... (I don't do hardware :D but I would've been convinced it was necessary)

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