From 82728f4ebb55f72f46e3a566fc648d33df9e5080 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Tue, 16 Dec 2025 23:00:12 +0100
Subject: [PATCH] C&T KBC: Implement unknown command B3h as a dummy command
 that only outputs the output buffer, fixes the Atari PC4.

---
 src/device/kbc_at.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/device/kbc_at.c b/src/device/kbc_at.c
index 36f299315..b2e027cd3 100644
--- a/src/device/kbc_at.c
+++ b/src/device/kbc_at.c
@@ -1751,6 +1751,13 @@ write_cmd_chips(void *priv, uint8_t val)
             dev->state     = STATE_KBC_PARAM;
             ret = 0;
             break;
+
+        case 0xb3: /* Unknown */
+            kbc_at_log("ATkbc: C&T - Unknown\n");
+            kbc_delay_to_ob(dev, dev->ob, 0, 0x00);
+            dev->pending++;
+            ret = 0;
+            break;
     }
 
     return ret;