From dbd04f09e868a597d6cb79ec5fd5a972df4a8410 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Sat, 25 Feb 2017 15:42:26 +0200
Subject: [PATCH] HBlank HDMA should start instantly when starting during
 HBlank. Fixes 3-D Ultra Pinball.

---
 Core/memory.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Core/memory.c b/Core/memory.c
index a13b3740..32a19aa7 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -577,6 +577,10 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 }
                 gb->hdma_on = (value & 0x80) == 0;
                 gb->hdma_on_hblank = (value & 0x80) != 0;
+                if (gb->hdma_on_hblank && (gb->io_registers[GB_IO_STAT] & 3) == 0) {
+                    gb->hdma_on = true;
+                    gb->hdma_cycles = 0;
+                }
                 gb->io_registers[GB_IO_HDMA5] = value;
                 gb->hdma_steps_left = (gb->io_registers[GB_IO_HDMA5] & 0x7F) + 1;
                 /* Todo: Verify this. Gambatte's DMA tests require this. */