Do you mean POST code 61 on the 7-segment display? I checked the BIOS source and it appears to be hanging when trying to initialize keyboard controller: https://github.com/skiselev/8088_bios/blob/fa … at_kbc.inc#L623
Which KBC chip did you use? From my experience Xi8088 is fairly picky, I’ve tried various different ones and the only controller that worked reliably was VIA VT82C42N.

I am also using the VIA VT82C42N. During testing, I also found that sometimes the system can successfully boot up when the battery is not installed and the default BIOS settings are loaded during cold boot.
If I remove the keyboard control chip, I can still enter the system by simply restarting it, or immediately shutting it down and then turning it back on.

There is another issue: after installing Windows 3.0 on the xi8088, the mouse cannot be driven. Has anyone successfully driven it? How did you do it? There is a mouse driver under DOS 6.22, and it works very well

Win3.0 runs very stably on xi8088, except that the mouse cannot be used. If the PS2 mouse cannot be driven, then only a serial mouse can be used, but it is expensive and relatively hard to find. I have seen someone use a PS2 to serial port adapter to achieve cost-effectiveness, and perhaps I will do the same in the future.
However, the card games on win3.0 can actually be played using a keyboard.

You could try making a project that uses a USB mouse as a COM device on the Xi8088.

USB mouse ISA adapter

Thank you for your suggestion. Perhaps I will try making one