diff --git a/src/wpc/alvgdmd.c b/src/wpc/alvgdmd.c
index 44a2b8a74..d3d5a614a 100644
--- a/src/wpc/alvgdmd.c
+++ b/src/wpc/alvgdmd.c
@@ -229,24 +229,38 @@ static PORT_WRITE_START( alvgdmd_writeport )
 	{ 0x00,0xff, port_w },
 PORT_END
 
-// Rasterization timing explanation (from reading the schematics, no verification on real hardware):
-//
-// CPU Clock @12MHz directly drives VCLOCK on PCA020 (Al's Garage Band) while it is divided by 4 on PCA020A (Mystery Castle & Pistol Poker)
-// - Rows: VCLOCK is divided by 384 per row: 256 for the 128 DOTCLOCK [U26/U21] + 128 for the COLLATCH [U23]
-// - Frame: row signal is divided by 128 to generate INT1 [U22/U26B], therefore after rasterizing 4 frames of 32 rows
-// 
-// Rasterized memory address A0..A14 is computed like this:
-// - A0 .. A3 is reseted at each row start with col address stored in the COLSTART register (as well as an initial bit shift which seems unused)
-// - A4 .. A8 is reseted each 4 frames (on INT1) with the frame address stored in the ROWSTART register
-// - A9 ..A10 is reseted each 4 frames (on INT1) either with 0 if PLANSENABLE=0 or with Bit67 of ROWSTART register on PCA020 or 01 on PCA020A
-// - A11..A14 is directly defined by the CODEPAGE register (can be changed directly while rasterizing, but I doubt this is ever done)
+/*
+ Rasterization explanation
+ [Disclaimer, the following has been deduced from schematics analysis/simulation, so maybe entirely wrong]
+
+ The board is built around discrete chips designed to rasterize frames with PWM shading: 
+ - Each row is rasterized 4 times, either with the same pattern if PLANS_ENABLE is false or from 4 block of RAM.
+ - Rasterized RAM address is built from the data latched in colstart and rowstart registers:
+    COLSTART0..2 - Bit shift (0..7) [unimplemented as it is unused by any hardware]
+    COLSTART3..6 - A0..A3
+    ROWTSART0..4 - A4..A8
+    GPLAN0..1    - A9..A10 (GPLAN0..1 is ROWSTART5..6 for PCA020, while for PCA020A GPLAN0=1 and GLPAN1=0)
+    CODEPAGE0..1 - A11..A14 (can be changed directly while rasterizing, but I doubt this is ever done)
+ - When rasterizing, in order to rasterize each row 4 times before moving to the next row, the row counter 
+   is built with GPLAN at its lowest bits, unlike the RAM address:
+    GPLAN0..1    - Counter Bit 0..1
+    ROWTSART0..4 - Counter Bit 2..6
+ - On PCA020A, CPU Clock @12MHz is divided by 4 to drive VCLOCK (Mystery Castle & Pistol Poker)
+    Each row is made up of 4 x 314 VCLOCK: 256 used to send the data (to generate 128 DOTCLOCK [U26/U21]), then 58 for the end of row COLLATCH,... [U23])
+    Each frame is made of 32 rows, after which the INT1 is generated [U22/U26B], therefore after rasterizing 4 frames of 32 rows, corresponding
+    to 4 x 32 x 314 = 40192 VCLOCK cycles, leading to a INT1 frequency of 74.6Hz and a refresh rate before PWM of 298.6Hz
+	 lucky1 measured on a real hardware a frequency of 74.5Hz which validates this.
+ - On PCA020, CPU Clock @12MHz directly drives VCLOCK (Al's Garage Band)
+    The digital logic is slightly different and likely lead to different cycle count.
+	 For the time being, we use the data gathered for PCA020A (which happens to look and play good)
+*/
 
 // Al's Garage Band Goes On A World Tour
 MACHINE_DRIVER_START(alvgdmd1)
   MDRV_CPU_ADD(I8051, 12000000)	/*12 Mhz*/
   MDRV_CPU_MEMORY(alvgdmd_readmem, alvgdmd_writemem)
   MDRV_CPU_PORTS(alvgdmd_readport, alvgdmd_writeport)
-  MDRV_CPU_PERIODIC_INT(dmd32_firq1, 12000000./(384.*128.)) // 244.14Hz for 4 frames => 976.56Hz per frame (!)
+  MDRV_CPU_PERIODIC_INT(dmd32_firq1, 12000000./(4.*32.*314.)) // FIXME likely wrong as the board is slightly different and the cycle count form PCA020A can not be taken as is
   MDRV_INTERLEAVE(50)
 MACHINE_DRIVER_END
 
@@ -255,7 +269,7 @@ MACHINE_DRIVER_START(alvgdmd2)
   MDRV_CPU_ADD(I8051, 12000000)	/*12 Mhz*/
   MDRV_CPU_MEMORY(alvgdmd_readmem, alvgdmd_writemem)
   MDRV_CPU_PORTS(alvgdmd_readport, alvgdmd_writeport)
-  MDRV_CPU_PERIODIC_INT(dmd32_firq2, 12000000./(4.*384.*128.)) // 61.03Hz for 4 frames => 244.14Hz per frame
+  MDRV_CPU_PERIODIC_INT(dmd32_firq2, 12000000./(4.*4.*32.*314.)) // 12MHz divided by 4, triggering INT1 every 4 (frames) x 32 (rows) x 314 (cycles per row)
   MDRV_INTERLEAVE(50)
 MACHINE_DRIVER_END
 
@@ -273,7 +287,7 @@ static void dmd32_init(struct sndbrdData *brdData) {
   memset(&dmdlocals, 0, sizeof(dmdlocals));
   dmdlocals.brdData = *brdData;
   dmd32_bank_w(0,0);			//Set DMD Bank to 0
-  dmdlocals.selsync = 1;		//Start Sync @ 1
+  dmdlocals.selsync = 1;	//Start Sync @ 1 (PCA020A only)
   core_dmd_pwm_init(&dmdlocals.pwm_state, 128, 32, IS_PCA020 ? CORE_DMD_PWM_FILTER_ALVG1 : CORE_DMD_PWM_FILTER_ALVG2);
 }
 
@@ -325,17 +339,17 @@ static INTERRUPT_GEN(dmd32_firq2) {
 	LOG(("Skipping INT1\n"));
 	return;
   }
+  // TODO if needed for backwards compatibility regarding colorization, previous implementation submitted a 16 shade frame made up of the 4 frames (if plans_enable = 0, four time the same frame) => 16 shades (with balanced luminance between frames)
   //static double prev; printf("DMD VBlank %8.5fms => %8.5fHz for 4 frames so %8.5fHz\n", timer_get_time() - prev, 1. / (timer_get_time() - prev), 4. / (timer_get_time() - prev)); prev = timer_get_time();
   LOG(("INT1 Pulse\n"));
   cpu_set_irq_line(dmdlocals.brdData.cpuNo, I8051_INT1_LINE, PULSE_LINE);
   assert((dmdlocals.colstart & 0x07) == 0); // Lowest 3 bits are actually loaded to the shift register, so it is possible to perform a dot shift, but we don't support it
   const UINT8* RAM = (UINT8*)dmd32RAM + (dmdlocals.vid_page << 11) + ((dmdlocals.colstart >> 3) & 0x0F);
   const unsigned int plan_mask = dmdlocals.plans_enable ? 0x7F : 0x1F; // either render 4 different frames or 4 times the same
-  // For backwards compatibility regarding colorization, previous implementation submitted a 16 shade frame made up of the 4 frames (if plans_enable = 0, four time the same frame) => 16 shades (with balanced luminance between frames)
-  core_dmd_submit_frame(&dmdlocals.pwm_state, RAM + (((dmdlocals.rowstart + 0x00) & plan_mask) << 4));
   core_dmd_submit_frame(&dmdlocals.pwm_state, RAM + (((dmdlocals.rowstart + 0x20) & plan_mask) << 4));
   core_dmd_submit_frame(&dmdlocals.pwm_state, RAM + (((dmdlocals.rowstart + 0x40) & plan_mask) << 4));
   core_dmd_submit_frame(&dmdlocals.pwm_state, RAM + (((dmdlocals.rowstart + 0x60) & plan_mask) << 4));
+  core_dmd_submit_frame(&dmdlocals.pwm_state, RAM + (((dmdlocals.rowstart + 0x00) & plan_mask) << 4));
 }
 
 PINMAME_VIDEO_UPDATE(alvgdmd_update) {
diff --git a/src/wpc/core.c b/src/wpc/core.c
index bdaa82656..ab2729287 100644
--- a/src/wpc/core.c
+++ b/src/wpc/core.c
@@ -3053,7 +3053,7 @@ void core_dmd_pwm_init(core_tDMDPWMState* dmd_state, const int width, const int
       dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_122_15) / sizeof(UINT16);
     }
     break;
-  case CORE_DMD_PWM_FILTER_ALVG1: // Alvin G. DMD Generation 1: 976Hz refresh rate / 15Hz low pass filter / 4 frames PWM pattern
+  case CORE_DMD_PWM_FILTER_ALVG1: // Alvin G. DMD Generation 1: 1194.4Hz refresh rate / 15Hz low pass filter / 4 frames PWM pattern
     if (dmd_state->legacyColorization)
     {
       // Al's Garage Band previous implementation would weight the first rasterized frame half less than the second and would only share this
@@ -3063,18 +3063,18 @@ void core_dmd_pwm_init(core_tDMDPWMState* dmd_state, const int width, const int
       dmd_state->fir_sum = 60000;
       dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_colorization_2_frames) / sizeof(UINT16);
     } else {
-      static const UINT16 fir_976_15[] = { 928, 1973, 4725, 8162, 10962, 12035, 10962, 8162, 4725, 1973, 928 };
-      dmd_state->fir_weights = fir_976_15;
+      static const UINT16 fir_1194_15[] = { 938, 1985, 4737, 8160, 10943, 12009, 10943, 8160, 4737, 1985, 938 };
+      dmd_state->fir_weights = fir_1194_15;
       dmd_state->fir_sum = 65535;
-      dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_976_15) / sizeof(UINT16);
+      dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_1194_15) / sizeof(UINT16);
     }
     break;
-  case CORE_DMD_PWM_FILTER_ALVG2: // Alvin G. DMD Generation 2: 244Hz refresh rate / 15Hz low pass filter / 4 frames PWM pattern
+  case CORE_DMD_PWM_FILTER_ALVG2: // Alvin G. DMD Generation 2: 298.6Hz refresh rate / 15Hz low pass filter / 4 frames PWM pattern
     {
-      static const UINT16 fir_244_15[] = { 521, 1451, 4187, 8183, 11798, 13255, 11798, 8183, 4187, 1451, 521 };
-      dmd_state->fir_weights = fir_244_15;
+      static const UINT16 fir_299_15[] = { 656, 1633, 4384, 8185, 11501, 12817, 11501, 8185, 4384, 1633, 656 };
+      dmd_state->fir_weights = fir_299_15;
       dmd_state->fir_sum = 65535;
-      dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_244_15) / sizeof(UINT16);
+      dmd_state->fir_size = dmd_state->nFrames = sizeof(fir_299_15) / sizeof(UINT16);
     }
     break;
   default:
diff --git a/src/wpc/dedmd.c b/src/wpc/dedmd.c
index 8224274b4..10058f4f8 100644
--- a/src/wpc/dedmd.c
+++ b/src/wpc/dedmd.c
@@ -88,7 +88,7 @@ MACHINE_DRIVER_END
 
  The board is built around a CRTC6845 [U9] which clock is driven by a custom PAL chip [U2]. This design allows to create 4 full shades: 
  - Each row is rasterized twice by the CRTC6845, first with a 500KHz clock, then with a 1MHz clock. To do so, the PAL chip toggles the 
-   clock divider on each HSYNC from the CRTC6845.
+   clock divider on each HSYNC from the CRTC6845. RA0 is likely used to toggle the clock divider inside U2.
  - Data is fed from RAM at offset X for first frame (double PWM length) then at X+0x200 for second frame (single PWM length). To do so,
    a memory mapping is applied to the linear rasterization performed by the CRTC6845, MA is the memory address output, RA is the character
    output. Character is used as the PWM frame selector and wired to bit 9 of the memory address allowing to render a line of each frame
@@ -99,10 +99,8 @@ MACHINE_DRIVER_END
     MA7      - A8      => DMD row highest bit [unimplemented in PinMame]
     RA0      - A9      => used to toggle between frame while rasterizing each row
     MA8..12  - A10..14
- - VSYNC signal from CRTC6845 is not used (not sure why), but the CURSOR signal is wired to U2, and the cursor register seems to always 
-   point to the start of the rasterization (so triggered when looping), maybe serving the VSYNC purpose and allowing to fire the FIRQ to
-   the DMD CPU.
- */
+ - ROWCLOCK is RA0 (so advanced one every 2 rasterized rows)
+  */
 static void dmd32_vblank(int which) {
   //static double prev; printf("DMD VBlank %8.5fms => %8.5fHz for 3 frames so %8.5fHz\n", timer_get_time() - prev, 1. / (timer_get_time() - prev), 3. / (timer_get_time() - prev)); prev = timer_get_time();
   // Store 2 next rasterized frame, as the CRTC is setup to render 2 contiguous full frames for each VBLANK