The PC/XT doesn't have a keyboard controller as we know it today. Starting with the AT, the "keyboard controller" is an actual microcontroller doing the keyboard interface and other minor system maintenance tasks like controlling the A20 gate or sending a reset signal to the 80286 processor to help it leave the protected mode. The keyboard interface and mainboard control on the PC/XT is build from discrete components interfaced to the ISA bus using the 8255 PPI (parallel peripheral interface) chip. It's possible that the landmark ROM is calling this chip the "keybaord controller".

Looking at the Landmark diag ROM manual (http://www.minuszerodegrees.net/supersoft_lan … rs%20Manual.pdf page 26) it says:

Note: Just as in the level 0 interrupt test, passing this test also requires the proper operation of other system board devices such as the 8259 Interrupt Controller, the 8288 Bus Controller (to process interrupts), and the 8255 Parallel Peripheral Interface controller (to receive scan codes from the Keyboard Controller).

I tried swapping each chip from another (possibly broken) board and I'm still getting the keyboard controller error but I'm wondering if I need to source another XT keyboard.

Hi, you can also get an older AT keyboard, maybe.
The one I have had a PC/AT switch on the backside/underside.
The switch really works, except that pressing the AT-specific keys causes some beep tones on my Nixdorf 8810 M35.

sndtst wrote on 2022-10-03, 01:57:

I tried swapping each chip from another (possibly broken) board and I'm still getting the keyboard controller error but I'm wondering if I need to source another XT keyboard.

Sounds like it. What keyboard are you using ?

Jo22 wrote on 2022-10-03, 02:03:

Hi, you can also get an older AT keyboard, maybe.
The one I have had a PC/AT switch on the backside/underside.
The switch really works, except that pressing the AT-specific keys causes some beep tones on my Nixdorf 8810 M35.

Yes !! The specific required KB controller on XT's is in the keyboard iirc. AT's have it on the motherboard (yes there is still one in AT KB's but is different).
Those AT keyboards with a switch for XT or AT modes work great !

sndtst wrote on 2022-10-03, 01:57:

and the 8255 Parallel Peripheral Interface controller (to receive scan codes from the Keyboard Controller).

Thanks for the quote. It explains that they are talking about the microcontroller inside the keyboard, not any chip on the board. So the keyboard connection (socket, cable) has to work properly, too, for this test to pass.

I was an idiot and was testing this with an AT keyboard. I dug through some things and found this Unitech XT keyboard and now the Keyboard controller test passes, but only every other time. On the first run it is successful, but then on the second run it fails only to pass again on the subsequent run. It's almost like running through the keyboard test is causing some bit to not get set back to zero. I have made more progress than I expected though so I'm going to try some of the other 8255/8258/8237 chips and see if it makes a difference. Thank you everyone for your help and advice.