The TMC PAT54PV has a PS/2 controller but an AT port.

src/machine/m_at_socket5.c

@@ -575,6 +575,8 @@ machine_at_pat54pv_init(const machine_t *model)
     machine_at_common_init(model);
 
     device_add(&opti5x7_device);
+
+    machine_force_ps2(1);
     device_add_params(machine_get_kbc_device(machine), (void *) model->kbc_params);
 
     if (fdc_current[0] == FDC_INTERNAL)

src/machine/machine_table.c

@@ -12857,7 +12857,7 @@ const machine_t machines[] = {
             .max_multi = 1.5
         },
         .bus_flags = MACHINE_VLB,
-        .flags = MACHINE_APM,
+        .flags = MACHINE_PS2_KBC | MACHINE_APM,
         .ram = {
             .min = 2048,
             .max = 65536,