From b4aea2f7689c9b50901f51912392f2791567c522 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Tue, 8 Aug 2023 03:52:09 +0200
Subject: [PATCH] The PIC timer is no longer used to latch all IRQ updates on
 XT, but only those after writes to the mask register, which are now delayed
 for the duration of 1 CPU cycles, making the PCjr boot again, fixes #3500.

---
 src/pic.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/src/pic.c b/src/pic.c
index 09ccf5d03..cb4cc109e 100644
--- a/src/pic.c
+++ b/src/pic.c
@@ -225,12 +225,7 @@ find_best_interrupt(pic_t *dev)
 static __inline void
 pic_update_pending_xt(void)
 {
-    if (find_best_interrupt(&pic) != -1) {
-        latched++;
-        if (latched == 1)
-            timer_on_auto(&pic_timer, 0.35);
-    } else if (latched == 0)
-        pic.int_pending = 0;
+    pic.int_pending = (find_best_interrupt(&pic) != -1);
 }
 
 static __inline void
@@ -248,11 +243,7 @@ pic_callback(void *priv)
 {
     pic_t *dev = (pic_t *) priv;
 
-    dev->int_pending = 1;
-
-    latched--;
-    if (latched > 0)
-        timer_on_auto(&pic_timer, 0.35);
+    update_pending();
 }
 
 void
@@ -501,7 +492,10 @@ pic_write(uint16_t addr, uint8_t val, void *priv)
                 break;
             case STATE_NONE:
                 dev->imr = val;
-                update_pending();
+                if (is286)
+                    update_pending();
+                else
+                    timer_on_auto(&pic_timer, .0 * ((10000000.0 * (double) xt_cpu_multi) / (double) cpu_s->rspeed));
                 break;
 
             default: