diff --git a/src/vid_s3.c b/src/vid_s3.c
index 0950e3c..57480db 100644
--- a/src/vid_s3.c
+++ b/src/vid_s3.c
@@ -276,10 +276,25 @@ static void s3_accel_out_fifo(s3_t *s3, uint16_t port, uint8_t val)
                 case 0xa2ea:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0x00ff0000) | (val << 16);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0x00ff0000) | (val << 16);
+                        else
+                                s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0x000000ff) | val;
+                }
                 break;
                 case 0xa2eb:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0xff000000) | (val << 24);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0xff000000) | (val << 24);
+                        else
+                                s3->accel.bkgd_color = (s3->accel.bkgd_color & ~0x0000ff00) | (val << 8);
+                        s3->accel.multifunc[0xe] ^= 0x10;
+                }
                 break;
 
                 case 0xa6e8:
@@ -299,10 +314,25 @@ static void s3_accel_out_fifo(s3_t *s3, uint16_t port, uint8_t val)
                 case 0xa6ea:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.frgd_color = (s3->accel.frgd_color & ~0x00ff0000) | (val << 16);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.frgd_color = (s3->accel.frgd_color & ~0x00ff0000) | (val << 16);
+                        else
+                                s3->accel.frgd_color = (s3->accel.frgd_color & ~0x000000ff) | val;
+                }
                 break;
                 case 0xa6eb:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.frgd_color = (s3->accel.frgd_color & ~0xff000000) | (val << 24);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.frgd_color = (s3->accel.frgd_color & ~0xff000000) | (val << 24);
+                        else
+                                s3->accel.frgd_color = (s3->accel.frgd_color & ~0x0000ff00) | (val << 8);
+                        s3->accel.multifunc[0xe] ^= 0x10;
+                }
                 break;
 
                 case 0xaae8:
@@ -322,10 +352,25 @@ static void s3_accel_out_fifo(s3_t *s3, uint16_t port, uint8_t val)
                 case 0xaaea:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0x00ff0000) | (val << 16);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0x00ff0000) | (val << 16);
+                        else
+                                s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0x000000ff) | val;
+                }
                 break;
                 case 0xaaeb:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0xff000000) | (val << 24);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0xff000000) | (val << 24);
+                        else
+                                s3->accel.wrt_mask = (s3->accel.wrt_mask & ~0x0000ff00) | (val << 8);
+                        s3->accel.multifunc[0xe] ^= 0x10;
+                }
                 break;
 
                 case 0xaee8:
@@ -345,10 +390,25 @@ static void s3_accel_out_fifo(s3_t *s3, uint16_t port, uint8_t val)
                 case 0xaeea:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.rd_mask = (s3->accel.rd_mask & ~0x00ff0000) | (val << 16);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.rd_mask = (s3->accel.rd_mask & ~0x00ff0000) | (val << 16);
+                        else
+                                s3->accel.rd_mask = (s3->accel.rd_mask & ~0x000000ff) | val;
+                }
                 break;
                 case 0xaeeb:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.rd_mask = (s3->accel.rd_mask & ~0xff000000) | (val << 24);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.rd_mask = (s3->accel.rd_mask & ~0xff000000) | (val << 24);
+                        else
+                                s3->accel.rd_mask = (s3->accel.rd_mask & ~0x0000ff00) | (val << 8);
+                        s3->accel.multifunc[0xe] ^= 0x10;
+                }
                 break;
 
                 case 0xb2e8:
@@ -368,10 +428,25 @@ static void s3_accel_out_fifo(s3_t *s3, uint16_t port, uint8_t val)
                 case 0xb2ea:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.color_cmp = (s3->accel.color_cmp & ~0x00ff0000) | (val << 16);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.color_cmp = (s3->accel.color_cmp & ~0x00ff0000) | (val << 16);
+                        else
+                                s3->accel.color_cmp = (s3->accel.color_cmp & ~0x000000ff) | val;
+                }
                 break;
                 case 0xb2eb:
                 if (s3->accel.multifunc[0xe] & 0x200)
                         s3->accel.color_cmp = (s3->accel.color_cmp & ~0xff000000) | (val << 24);
+                else if (s3->bpp == 3)
+                {
+                        if (s3->accel.multifunc[0xe] & 0x10)
+                                s3->accel.color_cmp = (s3->accel.color_cmp & ~0xff000000) | (val << 24);
+                        else
+                                s3->accel.color_cmp = (s3->accel.color_cmp & ~0x0000ff00) | (val << 8);
+                        s3->accel.multifunc[0xe] ^= 0x10;
+                }
                 break;
 
                 case 0xb6e8: