From 0aaf4f00fd2471a9fd5d9d0c94f27cafcde576fb Mon Sep 17 00:00:00 2001
From: Happy <Happy-yappH@users.noreply.github.com>
Date: Wed, 16 Nov 2016 17:42:22 -0700
Subject: [PATCH] n64:  Remove incorrect factor of two in VI and AI interrupt
 timing.

Also give priority to the current AI transfer when reporting transfer length.
---
 src/mame/drivers/n64.cpp |  2 +-
 src/mame/machine/n64.cpp | 26 +++++++++++++-------------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/mame/drivers/n64.cpp b/src/mame/drivers/n64.cpp
index 53b0bfcf0f0..4be88ddb49a 100644
--- a/src/mame/drivers/n64.cpp
+++ b/src/mame/drivers/n64.cpp
@@ -441,7 +441,7 @@ static MACHINE_CONFIG_START( n64, n64_mess_state )
 	/* video hardware */
 	MCFG_SCREEN_ADD("screen", RASTER)
 	/* Video DACRATE is for quarter pixels, so the horizontal is also given in quarter pixels.  However, the horizontal and vertical timing and sizing is adjustable by register and will be reset when the registers are written. */
-	MCFG_SCREEN_RAW_PARAMS(DACRATE_NTSC*2,3093,0,3093,525,0,525)
+	MCFG_SCREEN_RAW_PARAMS(DACRATE_NTSC,3093,0,3093,525,0,525)
 	//MCFG_SCREEN_REFRESH_RATE(60)
 	//MCFG_SCREEN_VBLANK_TIME(ATTOSECONDS_IN_USEC(0))
 	//MCFG_SCREEN_SIZE(640, 525)
diff --git a/src/mame/machine/n64.cpp b/src/mame/machine/n64.cpp
index 8171ab3e311..2a0360b5a2a 100644
--- a/src/mame/machine/n64.cpp
+++ b/src/mame/machine/n64.cpp
@@ -980,7 +980,7 @@ WRITE32_MEMBER( n64_periphs::dp_reg_w )
 TIMER_CALLBACK_MEMBER(n64_periphs::vi_scanline_callback)
 {
 	signal_rcp_interrupt(VI_INTERRUPT);
-	vi_scanline_timer->adjust(m_screen->time_until_pos(vi_intr >> 1));
+	vi_scanline_timer->adjust(m_screen->time_until_pos(vi_intr));
 }
 
 // Video Interface
@@ -995,7 +995,7 @@ void n64_periphs::vi_recalculate_resolution()
 
 	rectangle visarea = m_screen->visible_area();
 	// DACRATE is the quarter pixel clock and period will be for a field, not a frame
-	attoseconds_t period = (vi_hsync & 0xfff) * (vi_vsync & 0xfff) * HZ_TO_ATTOSECONDS(DACRATE_NTSC) / 2;
+	attoseconds_t period = (vi_hsync & 0xfff) * (vi_vsync & 0xfff) * HZ_TO_ATTOSECONDS(DACRATE_NTSC);
 
 	if (width == 0 || height == 0 || (vi_control & 3) == 0)
 	{
@@ -1116,7 +1116,7 @@ WRITE32_MEMBER( n64_periphs::vi_reg_w )
 
 		case 0x0c/4:        // VI_INTR_REG
 			vi_intr = data;
-			vi_scanline_timer->adjust(m_screen->time_until_pos(vi_intr)); // >> 1));
+			vi_scanline_timer->adjust(m_screen->time_until_pos(vi_intr));
 			break;
 
 		case 0x10/4:        // VI_CURRENT_REG
@@ -1268,7 +1268,7 @@ void n64_periphs::ai_dma()
 	ai_status |= 0x40000000;
 
 	// adjust the timer
-	period = attotime::from_hz(DACRATE_NTSC) * (ai_dacrate + 1) * (current->length / 4);
+	period = attotime::from_hz(DACRATE_NTSC) * (ai_dacrate + 1) * (current->length / 2);
 	ai_timer->adjust(period);
 }
 
@@ -1300,16 +1300,16 @@ READ32_MEMBER( n64_periphs::ai_reg_r )
 	{
 		case 0x04/4:        // AI_LEN_REG
 		{
-			if (ai_status & 0x80000001)
+			if (ai_status & 0x40000000)
+			{
+				double secs_left = (ai_timer->expire() - machine().time()).as_double();
+				ret = 2 * (uint32_t)(secs_left * (double)DACRATE_NTSC / (double)(ai_dacrate + 1));
+			}
+			else if (ai_status & 0x80000001)
 			{
 				ret = ai_len;
 			}
-			else if (ai_status & 0x40000000)
-			{
-				double secs_left = (ai_timer->expire() - machine().time()).as_double();
-				unsigned int samples_left = (uint32_t)(secs_left * (double)DACRATE_NTSC / (double)(ai_dacrate + 1));
-				ret = samples_left * 4;
-			}
+
 			else
 			{
 				ret = 0;
@@ -1340,12 +1340,12 @@ WRITE32_MEMBER( n64_periphs::ai_reg_w )
 			break;
 
 		case 0x04/4:        // AI_LEN_REG
-			ai_len = data & 0x3ffff;        // Hardware v2.0 has 18 bits, v1.0 has 15 bits
+			ai_len = data & 0x3fff8;        // Hardware v2.0 has 18 bits, v1.0 has 15 bits
 			ai_fifo_push(ai_dram_addr, ai_len);
 			break;
 
 		case 0x08/4:        // AI_CONTROL_REG
-			ai_control = data;
+			ai_control = data & 1;
 			break;
 
 		case 0x0c/4: