From: kub <derkub@gmail.com>
Date: Sat, 2 Mar 2024 09:36:49 +0000 (+0100)
Subject: core, slightly increase accuracy of some hw timers
X-Git-Tag: v2.00~107
X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=80f51a1d59e54aa6b628e5a514434bdd30b8b856;p=picodrive.git

core, slightly increase accuracy of some hw timers
---

diff --git a/pico/cd/memory.c b/pico/cd/memory.c
index 07578284..b13644b1 100644
--- a/pico/cd/memory.c
+++ b/pico/cd/memory.c
@@ -97,9 +97,9 @@ void m68k_comm_check(u32 a)
 
 u32 pcd_stopwatch_read(int sub)
 {
-  // ugh..
+  // ugh... stopwatch runs 384 cycles per step, divide by mult with inverse
   u32 d = sub ? SekCyclesDoneS68k() : pcd_cycles_m68k_to_s68k(SekCyclesDone());
-  d = (d - Pico_mcd->m.stopwatch_base_c) / 384;
+  d = ((d - Pico_mcd->m.stopwatch_base_c) * ((1LL << 32) / 384)) >> 32;
   return d & 0x0fff;
 }
 
diff --git a/pico/memory.c b/pico/memory.c
index c2a40f70..46e0bd4a 100644
--- a/pico/memory.c
+++ b/pico/memory.c
@@ -1092,7 +1092,7 @@ void ym2612_sync_timers(int z80_cycles, int mode_old, int mode_new)
        * Starting a timer takes place at the next tick, so xcycles needs to be
        * rounded up to that: t = next tick# = (xcycles / TICK_ZCYCLES) + 1
        */
-      unsigned t = ((xcycles * (((1<<20)/TIMER_A_TICK_ZCYCLES)+1))>>20) + 1;
+      unsigned t = ((xcycles * (((1LL<<32)/TIMER_A_TICK_ZCYCLES)+1))>>32) + 1;
       Pico.t.timer_a_next_oflow = t*TIMER_A_TICK_ZCYCLES + Pico.t.timer_a_step;
     }
   }
@@ -1115,7 +1115,7 @@ void ym2612_sync_timers(int z80_cycles, int mode_old, int mode_new)
        * reset by loading timer b. The first run of timer b after loading is
        * therefore shorter by up to 15 ticks.
        */
-      unsigned t = ((xcycles * (((1<<20)/TIMER_A_TICK_ZCYCLES)+1))>>20) + 1;
+      unsigned t = ((xcycles * (((1LL<<32)/TIMER_A_TICK_ZCYCLES)+1))>>32) + 1;
       int step = Pico.t.timer_b_step - TIMER_A_TICK_ZCYCLES*(t&15);
       Pico.t.timer_b_next_oflow = t*TIMER_A_TICK_ZCYCLES + step;
     }