ex-AntMiner BBB acting funny. Help?

[technix]

I bought an ex-AntMiner BeagleBone Black. It lacked the HDMI circuitry entirely with no pads and traces, it lacked all USB power switch and connectors although pads are still there, it lacked any buttons and the power jack, and the eMMC is replaced with 2Gb (512MB) raw NAND. I have restored all those missing parts that still have its pads and replaced the onboard NAND with a 64Gb (8GB) part.

Now the BBB in question refuses to boot at all, especially it refuses to do USB boot with the USB boot button pressed and no microSD card present. When I attached a J-Link, the CPU is trapped in Data Abort dead loop.

How to fix that?

[thinkfat]

You could try single-stepping the boot Rom. Also, There are a couple of memory locations in internal sram that store diagnostic codes from the boot process. They might help you find the issue.

[technix]

I think I have found the problem. On a real BBB the boot selector button pulls SYSBOOT[2] low from 5'b11100 to 5'b11000 to prioritize USB over MMC0, however on my board the default boot mode is already 5'b10011 prioritizing NAND so the button does nothing. I need to cut the boot selector button's ground pin and bodge in a pull up so the button makes 5'b10011 boot selection a 5'b10111, which no longer allows NAND but allows MMC0 and USB boot.

[technix]

After a quick trip under a knife and a bodge wire, WE GOT ENUMERATION!!!