diff --git a/src/vid_ati_mach64.c b/src/vid_ati_mach64.c
index 371638e..f6c7720 100644
--- a/src/vid_ati_mach64.c
+++ b/src/vid_ati_mach64.c
@@ -468,12 +468,12 @@ void mach64_recalctimings(svga_t *svga)
                         break;
                 }
 
-                svga->vrammask = mach64->vram_mask;
+                svga->vram_display_mask = mach64->vram_mask;
 //                pclog("mach64_recalctimings : frame %i,%i disp %i,%i vsync at %i rowoffset %i pixel clock %f MA %08X\n", svga->htotal, svga->vtotal, svga->hdisp, svga->dispend, svga->vsyncstart, svga->rowoffset, svga->clock, svga->ma);
         }
         else
         {
-                svga->vrammask = (mach64->regs[0x36] & 0x01) ? mach64->vram_mask : 0x3ffff;
+                svga->vram_display_mask = (mach64->regs[0x36] & 0x01) ? mach64->vram_mask : 0x3ffff;
         }
 }
 
diff --git a/src/vid_cl5429.c b/src/vid_cl5429.c
index 6616b59..15a805d 100644
--- a/src/vid_cl5429.c
+++ b/src/vid_cl5429.c
@@ -350,9 +350,10 @@ void gd5429_write_linear(uint32_t addr, uint8_t val, void *p)
         {
                 addr <<= 2;
         }
-        addr &= 0x7fffff;
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
 //        if (svga_output) pclog("%08X\n", addr);
         svga->changedvram[addr >> 12] = changeframecount;
         
@@ -595,16 +596,16 @@ void gd5429_start_blit(uint32_t cpu_dat, int count, void *p)
                         switch (gd5429->blt.mode & 0xc0)
                         {
                                 case 0x00:
-                                src = svga->vram[gd5429->blt.src_addr & svga->vrammask];
+                                src = svga->vram[gd5429->blt.src_addr & svga->vram_mask];
                                 gd5429->blt.src_addr += ((gd5429->blt.mode & 0x01) ? -1 : 1);
                                 mask = 1;
                                 break;
                                 case 0x40:
-                                src = svga->vram[(gd5429->blt.src_addr & (svga->vrammask & ~7)) | (gd5429->blt.dst_addr & 7)];
+                                src = svga->vram[(gd5429->blt.src_addr & (svga->vram_mask & ~7)) | (gd5429->blt.dst_addr & 7)];
                                 mask = 1;
                                 break;
                                 case 0x80:
-                                mask = svga->vram[gd5429->blt.src_addr & svga->vrammask] & (0x80 >> gd5429->blt.x_count);
+                                mask = svga->vram[gd5429->blt.src_addr & svga->vram_mask] & (0x80 >> gd5429->blt.x_count);
                                 src = mask ? gd5429->blt.fg_col : gd5429->blt.bg_col;
                                 gd5429->blt.x_count++;
                                 if (gd5429->blt.x_count == 8)
@@ -614,16 +615,16 @@ void gd5429_start_blit(uint32_t cpu_dat, int count, void *p)
                                 }
                                 break;
                                 case 0xc0:
-                                mask = svga->vram[gd5429->blt.src_addr & svga->vrammask] & (0x80 >> (gd5429->blt.dst_addr & 7));
+                                mask = svga->vram[gd5429->blt.src_addr & svga->vram_mask] & (0x80 >> (gd5429->blt.dst_addr & 7));
                                 src = mask ? gd5429->blt.fg_col : gd5429->blt.bg_col;
                                 break;
                         }
                         count--;                        
                 }
-                dst = svga->vram[gd5429->blt.dst_addr & svga->vrammask];
-                svga->changedvram[(gd5429->blt.dst_addr & svga->vrammask) >> 12] = changeframecount;
+                dst = svga->vram[gd5429->blt.dst_addr & svga->vram_mask];
+                svga->changedvram[(gd5429->blt.dst_addr & svga->vram_mask) >> 12] = changeframecount;
                
-                pclog("Blit %i,%i %06X %06X  %06X %02X %02X  %02X %02X ", gd5429->blt.width, gd5429->blt.height_internal, gd5429->blt.src_addr, gd5429->blt.dst_addr, gd5429->blt.src_addr & svga->vrammask, svga->vram[gd5429->blt.src_addr & svga->vrammask], 0x80 >> (gd5429->blt.dst_addr & 7), src, dst);
+                pclog("Blit %i,%i %06X %06X  %06X %02X %02X  %02X %02X ", gd5429->blt.width, gd5429->blt.height_internal, gd5429->blt.src_addr, gd5429->blt.dst_addr, gd5429->blt.src_addr & svga->vram_mask, svga->vram[gd5429->blt.src_addr & svga->vram_mask], 0x80 >> (gd5429->blt.dst_addr & 7), src, dst);
                 switch (gd5429->blt.rop)
                 {
                         case 0x00: dst = 0;             break;
@@ -647,7 +648,7 @@ void gd5429_start_blit(uint32_t cpu_dat, int count, void *p)
                 
                 if ((gd5429->blt.width_backup - gd5429->blt.width) >= (gd5429->blt.mask & 7) &&
                     !((gd5429->blt.mode & 0x08) && !mask))
-                        svga->vram[gd5429->blt.dst_addr & svga->vrammask] = dst;
+                        svga->vram[gd5429->blt.dst_addr & svga->vram_mask] = dst;
                 
                 gd5429->blt.dst_addr += ((gd5429->blt.mode & 0x01) ? -1 : 1);
                 
diff --git a/src/vid_et4000w32.c b/src/vid_et4000w32.c
index 97fca5f..201701b 100644
--- a/src/vid_et4000w32.c
+++ b/src/vid_et4000w32.c
@@ -554,7 +554,7 @@ void et4000w32p_mmu_write(uint32_t addr, uint8_t val, void *p)
                 }
                 else
                 {
-                        if ((addr&0x1fff) + et4000->mmu.base[bank] < svga->vram_limit)
+                        if ((addr&0x1fff) + et4000->mmu.base[bank] < svga->vram_max)
                         {
                                 svga->vram[(addr & 0x1fff) + et4000->mmu.base[bank]] = val;
                                 svga->changedvram[((addr & 0x1fff) + et4000->mmu.base[bank]) >> 12] = changeframecount;
@@ -614,7 +614,7 @@ uint8_t et4000w32p_mmu_read(uint32_t addr, void *p)
                         /*???*/
                         return temp;
                 }
-                if ((addr&0x1fff) + et4000->mmu.base[bank] >= svga->vram_limit)
+                if ((addr&0x1fff) + et4000->mmu.base[bank] >= svga->vram_max)
                         return 0xff;
                 return svga->vram[(addr&0x1fff) + et4000->mmu.base[bank]];
                 
diff --git a/src/vid_oti067.c b/src/vid_oti067.c
index e528e01..4a2cbc8 100644
--- a/src/vid_oti067.c
+++ b/src/vid_oti067.c
@@ -65,13 +65,13 @@ void oti067_out(uint16_t addr, uint8_t val, void *p)
                 switch (oti067->index)
                 {
                         case 0xD:
-                        svga->vrammask = (val & 0xc) ? oti067->vram_mask : 0x3ffff;
+                        svga->vram_display_mask = (val & 0xc) ? oti067->vram_mask : 0x3ffff;
                         if ((val & 0x80) && oti067->vram_size == 256)
                                 mem_mapping_disable(&svga->mapping);
                         else
                                 mem_mapping_enable(&svga->mapping);
                         if (!(val & 0x80))
-                                svga->vrammask = 0x3ffff;
+                                svga->vram_display_mask = 0x3ffff;
                         break;
                         case 0x11:
                         svga->read_bank = (val & 0xf) * 65536;
diff --git a/src/vid_s3.c b/src/vid_s3.c
index d8f5fe9..653eb76 100644
--- a/src/vid_s3.c
+++ b/src/vid_s3.c
@@ -818,7 +818,7 @@ void s3_out(uint16_t addr, uint8_t val, void *p)
                         s3->ma_ext = (s3->ma_ext & 0x1c) | ((val & 0x30) >> 4);
                         break;
                         case 0x32:
-                        svga->vrammask = (val & 0x40) ? 0x3ffff : s3->vram_mask;
+                        svga->vram_display_mask = (val & 0x40) ? 0x3ffff : s3->vram_mask;
                         break;
                                                 
                         case 0x50:
@@ -2222,6 +2222,29 @@ static void *s3_init(char *bios_fn, int chip)
                    s3_hwcursor_draw,
                    NULL);
 
+        svga->decode_mask = (4 << 20) - 1;
+        switch (vram)
+        {
+                case 0: /*512kb*/
+                svga->vram_mask = (1 << 19) - 1;
+                svga->vram_max = 2 << 20;
+                break;
+                case 1: /*1MB*/
+                /*VRAM in first MB, mirrored in 2nd MB, 3rd and 4th MBs are open bus*/
+                svga->vram_mask = (1 << 20) - 1;
+                svga->vram_max = 2 << 20;
+                break;
+                case 2: default: /*2MB*/
+                /*VRAM in first 2 MB, 3rd and 4th MBs are open bus*/
+                svga->vram_mask = (2 << 20) - 1;
+                svga->vram_max = 2 << 20;
+                break;
+                case 4: /*4MB*/
+                svga->vram_mask = (4 << 20) - 1;
+                svga->vram_max = 4 << 20;
+                break;
+        }
+                
         if (PCI)
                 svga->crtc[0x36] = 2 | (3 << 2) | (1 << 4) | (vram_sizes[vram] << 5);
         else
diff --git a/src/vid_s3_virge.c b/src/vid_s3_virge.c
index 625901b..9451755 100644
--- a/src/vid_s3_virge.c
+++ b/src/vid_s3_virge.c
@@ -370,7 +370,7 @@ static void s3_virge_out(uint16_t addr, uint8_t val, void *p)
                         break;
                         case 0x32:
                         if ((svga->crtc[0x67] & 0xc) != 0xc)
-                                svga->vrammask = (val & 0x40) ? 0x3ffff : ((virge->memory_size << 20) - 1);
+                                svga->vram_display_mask = (val & 0x40) ? 0x3ffff : ((virge->memory_size << 20) - 1);
                         s3_virge_update_irqs(virge);
                         break;
                         
@@ -583,7 +583,7 @@ static void s3_virge_recalctimings(svga_t *svga)
                 {
                         svga->rowoffset = (svga->rowoffset * 3) / 4; /*Hack*/
                 }
-                svga->vrammask = (svga->crtc[0x32] & 0x40) ? 0x3ffff : ((virge->memory_size << 20) - 1);
+                svga->vram_display_mask = (svga->crtc[0x32] & 0x40) ? 0x3ffff : ((virge->memory_size << 20) - 1);
 //pclog("VGA mode   x_disp=%i dispend=%i vtotal=%i\n", svga->hdisp, svga->dispend, svga->vtotal);
         }
         else /*Streams mode*/
@@ -631,7 +631,7 @@ static void s3_virge_recalctimings(svga_t *svga)
                         svga->render = svga_render_32bpp_highres; 
                         break;
                 }
-                svga->vrammask = (virge->memory_size << 20) - 1;
+                svga->vram_display_mask = (virge->memory_size << 20) - 1;
         }
 
         if (((svga->miscout >> 2) & 3) == 3)
diff --git a/src/vid_svga.c b/src/vid_svga.c
index 7e9f7e7..6b45d84 100644
--- a/src/vid_svga.c
+++ b/src/vid_svga.c
@@ -483,7 +483,7 @@ void svga_poll(void *p)
                 {
                         svga->hdisp_on=1;
                         
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
                         if (svga->firstline == 2000)
                         {
                                 svga->firstline = svga->displine;
@@ -561,7 +561,7 @@ void svga_poll(void *p)
                                 svga->maback += (svga->rowoffset << 3);
                                 if (svga->interlace)
                                         svga->maback += (svga->rowoffset << 3);
-                                svga->maback &= svga->vrammask;
+                                svga->maback &= svga->vram_display_mask;
                                 svga->ma = svga->maback;
                         }
                         else
@@ -594,7 +594,7 @@ void svga_poll(void *p)
                                 svga->fullchange = 2;
                         svga->blink++;
 
-                        for (x = 0; x < (svga->vram_limit >> 12); x++) 
+                        for (x = 0; x < ((svga->vram_mask+1) >> 12); x++) 
                         {
                                 if (svga->changedvram[x]) 
                                         svga->changedvram[x]--;
@@ -728,8 +728,10 @@ int svga_init(svga_t *svga, void *p, int memsize,
         svga->dispofftime = 1000 * (1 << TIMER_SHIFT);        
         svga->bpp = 8;
         svga->vram = malloc(memsize);
-        svga->vram_limit = memsize;
-        svga->vrammask = memsize - 1;
+        svga->vram_max = memsize;
+        svga->vram_display_mask = memsize - 1;
+        svga->vram_mask = memsize - 1;
+        svga->decode_mask = 0x7fffff;
         svga->changedvram = malloc(/*(memsize >> 12) << 1*/0x800000 >> 12);
         svga->recalctimings_ex = recalctimings_ex;
         svga->video_in  = video_in;
@@ -790,10 +792,12 @@ void svga_write(uint32_t addr, uint8_t val, void *p)
         {
                 addr<<=2;
         }
-        addr &= 0x7fffff;
+        addr &= svga->decode_mask;
 
-        if (addr >= svga->vram_limit)
+        if (addr >= svga->vram_max)
                 return;
+        
+        addr &= svga->vram_mask;
 
         if (svga_output) pclog("%08X (%i, %i) %02X %i %i %i %02X\n", addr, addr & 1023, addr >> 10, val, writemask2, svga->writemode, svga->chain4, svga->gdcreg[8]);
         svga->changedvram[addr >> 12] = changeframecount;
@@ -954,19 +958,20 @@ uint8_t svga_read(uint32_t addr, void *p)
         
         egareads++;
 //        pclog("Readega %06X   ",addr);
+
         addr &= svga->banked_mask;
         addr += svga->read_bank;
-
-        latch_addr = (addr << 2) & 0x7fffff;
+                
+        latch_addr = (addr << 2) & svga->decode_mask;
         
 //        pclog("%05X %i %04X:%04X %02X %02X %i\n",addr,svga->chain4,CS,pc, vram[addr & 0x7fffff], vram[(addr << 2) & 0x7fffff], svga->readmode);
 //        pclog("%i\n", svga->readmode);
         if (svga->chain4 || svga->fb_only) 
         { 
-                addr &= 0x7fffff;
-                if (addr >= svga->vram_limit)
-                   return 0xff;
-                return svga->vram[addr];
+                addr &= svga->decode_mask;
+                if (addr >= svga->vram_max)
+                        return 0xff;
+                return svga->vram[addr & svga->vram_mask];
         }
         else if (svga->chain2_read)
         {
@@ -976,22 +981,27 @@ uint8_t svga_read(uint32_t addr, void *p)
         }
         else
                 addr<<=2;
+
+        addr &= svga->decode_mask;
         
-        addr &= 0x7fffff;
-        
-        if (addr >= svga->vram_limit)
-           return 0xff;
-        
-        if (latch_addr < svga->vram_limit)
+        if (latch_addr >= svga->vram_max)
+        {
+                svga->la = svga->lb = svga->lc = svga->ld = 0xff;
+        }
+        else
         {   
+                latch_addr &= svga->vram_mask;
                 svga->la = svga->vram[latch_addr];
                 svga->lb = svga->vram[latch_addr | 0x1];
                 svga->lc = svga->vram[latch_addr | 0x2];
                 svga->ld = svga->vram[latch_addr | 0x3];
         }
-        else
-                svga->la = svga->lb = svga->lc = svga->ld = 0xff;
 
+        if (addr >= svga->vram_max)
+                return 0xff;
+        
+        addr &= svga->vram_mask;
+        
         if (svga->readmode)
         {
                 temp   = svga->la;
@@ -1009,6 +1019,7 @@ uint8_t svga_read(uint32_t addr, void *p)
                 return ~(temp | temp2 | temp3 | temp4);
         }
 //pclog("Read %02X %04X %04X\n",vram[addr|svga->readplane],addr,svga->readplane);
+
         return svga->vram[addr | readplane];
 }
 
@@ -1043,9 +1054,10 @@ void svga_write_linear(uint32_t addr, uint8_t val, void *p)
         {
                 addr<<=2;
         }
-        addr &= 0x7fffff;
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
         if (svga_output) pclog("%08X\n", addr);
         svga->changedvram[addr >> 12]=changeframecount;
         
@@ -1206,10 +1218,10 @@ uint8_t svga_read_linear(uint32_t addr, void *p)
         
         if (svga->chain4 || svga->fb_only) 
         { 
-                addr &= 0x7fffff;
-                if (addr >= svga->vram_limit)
-                   return 0xff;
-                return svga->vram[addr & 0x7fffff]; 
+                addr &= svga->decode_mask;
+                if (addr >= svga->vram_max)
+                        return 0xff;
+                return svga->vram[addr & svga->vram_mask]; 
         }
         else if (svga->chain2_read)
         {
@@ -1220,10 +1232,12 @@ uint8_t svga_read_linear(uint32_t addr, void *p)
         else
                 addr<<=2;
 
-        addr &= 0x7fffff;
+        addr &= svga->decode_mask;
         
-        if (addr >= svga->vram_limit)
-           return 0xff;
+        if (addr >= svga->vram_max)
+                return 0xff;
+                
+        addr &= svga->vram_mask;
 
         svga->la = svga->vram[addr];
         svga->lb = svga->vram[addr | 0x1];
@@ -1296,9 +1310,10 @@ void svga_writew(uint32_t addr, uint16_t val, void *p)
 
         if (svga_output) pclog("svga_writew: %05X ", addr);
         addr = (addr & svga->banked_mask) + svga->write_bank;
-        addr &= 0x7FFFFF;        
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
         if (svga_output) pclog("%08X (%i, %i) %04X\n", addr, addr & 1023, addr >> 10, val);
         svga->changedvram[addr >> 12] = changeframecount;
         *(uint16_t *)&svga->vram[addr] = val;
@@ -1324,9 +1339,10 @@ void svga_writel(uint32_t addr, uint32_t val, void *p)
 
         if (svga_output) pclog("svga_writel: %05X ", addr);
         addr = (addr & svga->banked_mask) + svga->write_bank;
-        addr &= 0x7FFFFF;
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
         if (svga_output) pclog("%08X (%i, %i) %08X\n", addr, addr & 1023, addr >> 10, val);
         
         svga->changedvram[addr >> 12] = changeframecount;
@@ -1347,11 +1363,12 @@ uint16_t svga_readw(uint32_t addr, void *p)
 
 //        pclog("Readw %05X ", addr);
         addr = (addr & svga->banked_mask) + svga->read_bank;
-        addr &= 0x7FFFFF;
+        addr &= svga->decode_mask;
 //        pclog("%08X %04X\n", addr, *(uint16_t *)&vram[addr]);
-        if (addr >= svga->vram_limit) return 0xffff;
+        if (addr >= svga->vram_max)
+                return 0xffff;
         
-        return *(uint16_t *)&svga->vram[addr];
+        return *(uint16_t *)&svga->vram[addr & svga->vram_mask];
 }
 
 uint32_t svga_readl(uint32_t addr, void *p)
@@ -1368,11 +1385,12 @@ uint32_t svga_readl(uint32_t addr, void *p)
 
 //        pclog("Readl %05X ", addr);
         addr = (addr & svga->banked_mask) + svga->read_bank;
-        addr &= 0x7FFFFF;
+        addr &= svga->decode_mask;
 //        pclog("%08X %08X\n", addr, *(uint32_t *)&vram[addr]);
-        if (addr >= svga->vram_limit) return 0xffffffff;
+        if (addr >= svga->vram_max)
+                return 0xffffffff;
         
-        return *(uint32_t *)&svga->vram[addr];
+        return *(uint32_t *)&svga->vram[addr & svga->vram_mask];
 }
 
 void svga_writew_linear(uint32_t addr, uint16_t val, void *p)
@@ -1392,9 +1410,10 @@ void svga_writew_linear(uint32_t addr, uint16_t val, void *p)
         cycles_lost += video_timing_w;
 
 	if (svga_output) pclog("Write LFBw %08X %04X\n", addr, val);
-        addr &= 0x7FFFFF;
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
         svga->changedvram[addr >> 12] = changeframecount;
         *(uint16_t *)&svga->vram[addr] = val;
 }
@@ -1418,9 +1437,10 @@ void svga_writel_linear(uint32_t addr, uint32_t val, void *p)
         cycles_lost += video_timing_l;
 
 	if (svga_output) pclog("Write LFBl %08X %08X\n", addr, val);
-        addr &= 0x7fffff;
-        if (addr >= svga->vram_limit)
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
                 return;
+        addr &= svga->vram_mask;
         svga->changedvram[addr >> 12] = changeframecount;
         *(uint32_t *)&svga->vram[addr] = val;
 }
@@ -1437,10 +1457,11 @@ uint16_t svga_readw_linear(uint32_t addr, void *p)
         cycles -= video_timing_w;
         cycles_lost += video_timing_w;
 
-        addr &= 0x7FFFFF;
-        if (addr >= svga->vram_limit) return 0xffff;
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
+                return 0xffff;
         
-        return *(uint16_t *)&svga->vram[addr];
+        return *(uint16_t *)&svga->vram[addr & svga->vram_mask];
 }
 
 uint32_t svga_readl_linear(uint32_t addr, void *p)
@@ -1455,10 +1476,11 @@ uint32_t svga_readl_linear(uint32_t addr, void *p)
         cycles -= video_timing_l;
         cycles_lost += video_timing_l;
 
-        addr &= 0x7FFFFF;
-        if (addr >= svga->vram_limit) return 0xffffffff;
+        addr &= svga->decode_mask;
+        if (addr >= svga->vram_max)
+                return 0xffffffff;
 
-        return *(uint32_t *)&svga->vram[addr];
+        return *(uint32_t *)&svga->vram[addr & svga->vram_mask];
 }
 
 
diff --git a/src/vid_svga.h b/src/vid_svga.h
index 9dbacd7..f3455a3 100644
--- a/src/vid_svga.h
+++ b/src/vid_svga.h
@@ -15,7 +15,18 @@ typedef struct svga_t
         uint8_t miscout;
         int vidclock;
 
-        uint32_t vram_limit;
+        /*The three variables below allow us to implement memory maps like that seen on a 1MB Trio64 :
+          0MB-1MB - VRAM
+          1MB-2MB - VRAM mirror
+          2MB-4MB - open bus
+          4MB-xMB - mirror of above
+          
+          For the example memory map, decode_mask would be 4MB-1 (4MB address space), vram_max would be 2MB
+          (present video memory only responds to first 2MB), vram_mask would be 1MB-1 (video memory wraps at 1MB)
+        */
+        uint32_t decode_mask;
+        uint32_t vram_max;
+        uint32_t vram_mask;
         
         uint8_t la, lb, lc, ld;
         
@@ -71,7 +82,7 @@ typedef struct svga_t
         
         uint8_t *vram;
         uint8_t *changedvram;
-        int vrammask;
+        uint32_t vram_display_mask;
         uint32_t banked_mask;
 
         uint32_t write_bank, read_bank;
diff --git a/src/vid_svga_render.c b/src/vid_svga_render.c
index 173fe6c..4e7af2b 100644
--- a/src/vid_svga_render.c
+++ b/src/vid_svga_render.c
@@ -51,8 +51,8 @@ void svga_render_text_40(svga_t *svga)
                 for (x = 0; x < svga->hdisp; x += xinc)
                 {
                         drawcursor = ((svga->ma == svga->ca) && svga->con && svga->cursoron);
-                        chr  = svga->vram[(svga->ma << 1) & svga->vrammask];
-                        attr = svga->vram[((svga->ma << 1) + 1) & svga->vrammask];
+                        chr  = svga->vram[(svga->ma << 1) & svga->vram_display_mask];
+                        attr = svga->vram[((svga->ma << 1) + 1) & svga->vram_display_mask];
                         if (attr & 8) charaddr = svga->charsetb + (chr * 128);
                         else          charaddr = svga->charseta + (chr * 128);
 
@@ -91,7 +91,7 @@ void svga_render_text_40(svga_t *svga)
                         svga->ma += 4; 
                         p += xinc;
                 }
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -114,8 +114,8 @@ void svga_render_text_80(svga_t *svga)
                 for (x = 0; x < svga->hdisp; x += xinc)
                 {
                         drawcursor = ((svga->ma == svga->ca) && svga->con && svga->cursoron);
-                        chr  = svga->vram[(svga->ma << 1) & svga->vrammask];
-                        attr = svga->vram[((svga->ma << 1) + 1) & svga->vrammask];
+                        chr  = svga->vram[(svga->ma << 1) & svga->vram_display_mask];
+                        attr = svga->vram[((svga->ma << 1) + 1) & svga->vram_display_mask];
                         if (attr & 8) charaddr = svga->charsetb + (chr * 128);
                         else          charaddr = svga->charseta + (chr * 128);
 
@@ -154,7 +154,7 @@ void svga_render_text_80(svga_t *svga)
                         svga->ma += 4; 
                         p += xinc;
                 }
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -192,7 +192,7 @@ void svga_render_2bpp_lowres(svga_t *svga)
                                 dat[1] = svga->vram[(svga->ma << 1) + 1];
                         }
                         svga->ma += 4; 
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
 
                         p[0]  = p[1]  = svga->pallook[svga->egapal[(dat[0] >> 6) & 3]];
                         p[2]  = p[3]  = svga->pallook[svga->egapal[(dat[0] >> 4) & 3]];
@@ -242,7 +242,7 @@ void svga_render_2bpp_highres(svga_t *svga)
                                 dat[1] = svga->vram[(svga->ma << 1) + 1];
                         }
                         svga->ma += 4; 
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
 
                         p[0] = svga->pallook[svga->egapal[(dat[0] >> 6) & 3]];
                         p[1] = svga->pallook[svga->egapal[(dat[0] >> 4) & 3]];
@@ -277,7 +277,7 @@ void svga_render_4bpp_lowres(svga_t *svga)
 
                         *(uint32_t *)(&edat[0]) = *(uint32_t *)(&svga->vram[svga->ma]);                        
                         svga->ma += 4; 
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
 
                         dat = edatlookup[edat[0] >> 6][edat[1] >> 6] | (edatlookup[edat[2] >> 6][edat[3] >> 6] << 2);
                         p[0]  = p[1]  = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
@@ -326,7 +326,7 @@ void svga_render_4bpp_highres(svga_t *svga)
                         else
                                 *(uint32_t *)(&edat[0]) = *(uint32_t *)(&svga->vram[svga->ma]);
                         svga->ma += 4;
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
 
                         dat = edatlookup[edat[0] >> 6][edat[1] >> 6] | (edatlookup[edat[2] >> 6][edat[3] >> 6] << 2);
                         p[0] = svga->pallook[svga->egapal[(dat >> 4) & svga->plane_mask]];
@@ -360,7 +360,7 @@ void svga_render_8bpp_lowres(svga_t *svga)
                                                                 
                 for (x = 0; x <= svga->hdisp; x += 8)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vram_display_mask]);
                         
                         p[0] = p[1] = svga->pallook[dat & 0xff];
                         p[2] = p[3] = svga->pallook[(dat >> 8) & 0xff];
@@ -370,7 +370,7 @@ void svga_render_8bpp_lowres(svga_t *svga)
                         svga->ma += 4;
                         p += 8;
                 }
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -389,13 +389,13 @@ void svga_render_8bpp_highres(svga_t *svga)
                 for (x = 0; x <= svga->hdisp; x += 8)
                 {
                         uint32_t dat;
-                        dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vram_display_mask]);
                         p[0] = svga->pallook[dat & 0xff];
                         p[1] = svga->pallook[(dat >> 8) & 0xff];
                         p[2] = svga->pallook[(dat >> 16) & 0xff];
                         p[3] = svga->pallook[(dat >> 24) & 0xff];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 4) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 4) & svga->vram_display_mask]);
                         p[4] = svga->pallook[dat & 0xff];
                         p[5] = svga->pallook[(dat >> 8) & 0xff];
                         p[6] = svga->pallook[(dat >> 16) & 0xff];
@@ -404,7 +404,7 @@ void svga_render_8bpp_highres(svga_t *svga)
                         svga->ma += 8;
                         p += 8;
                 }
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -422,18 +422,18 @@ void svga_render_15bpp_lowres(svga_t *svga)
                
                 for (x = 0; x <= svga->hdisp; x += 4)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vram_display_mask]);
 
                         p[x]     = video_15to32[dat & 0xffff];
                         p[x + 1] = video_15to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vram_display_mask]);
 
                         p[x]     = video_15to32[dat & 0xffff];
                         p[x + 1] = video_15to32[dat >> 16];
                 }
                 svga->ma += x << 1; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -451,24 +451,24 @@ void svga_render_15bpp_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x += 8)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vram_display_mask]);
                         p[x]     = video_15to32[dat & 0xffff];
                         p[x + 1] = video_15to32[dat >> 16];
                         
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vram_display_mask]);
                         p[x + 2] = video_15to32[dat & 0xffff];
                         p[x + 3] = video_15to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 8) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 8) & svga->vram_display_mask]);
                         p[x + 4] = video_15to32[dat & 0xffff];
                         p[x + 5] = video_15to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 12) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 12) & svga->vram_display_mask]);
                         p[x + 6] = video_15to32[dat & 0xffff];
                         p[x + 7] = video_15to32[dat >> 16];
                 }
                 svga->ma += x << 1; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -486,18 +486,18 @@ void svga_render_16bpp_lowres(svga_t *svga)
                
                 for (x = 0; x <= svga->hdisp; x += 4)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vram_display_mask]);
 
                         p[x]     = video_16to32[dat & 0xffff];
                         p[x + 1] = video_16to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vram_display_mask]);
 
                         p[x]     = video_16to32[dat & 0xffff];
                         p[x + 1] = video_16to32[dat >> 16];
                 }
                 svga->ma += x << 1; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -515,24 +515,24 @@ void svga_render_16bpp_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x += 8)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1)) & svga->vram_display_mask]);
                         p[x]     = video_16to32[dat & 0xffff];
                         p[x + 1] = video_16to32[dat >> 16];
                         
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 4) & svga->vram_display_mask]);
                         p[x + 2] = video_16to32[dat & 0xffff];
                         p[x + 3] = video_16to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 8) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 8) & svga->vram_display_mask]);
                         p[x + 4] = video_16to32[dat & 0xffff];
                         p[x + 5] = video_16to32[dat >> 16];
 
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 12) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 1) + 12) & svga->vram_display_mask]);
                         p[x + 6] = video_16to32[dat & 0xffff];
                         p[x + 7] = video_16to32[dat >> 16];
                 }
                 svga->ma += x << 1; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -553,7 +553,7 @@ void svga_render_24bpp_lowres(svga_t *svga)
                 {
                         fg = svga->vram[svga->ma] | (svga->vram[svga->ma + 1] << 8) | (svga->vram[svga->ma + 2] << 16);
                         svga->ma += 3; 
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
                         ((uint32_t *)buffer32->line[svga->displine])[(x << 1) + offset] = ((uint32_t *)buffer32->line[svga->displine])[(x << 1) + 1 + offset] = fg;
                 }
         }
@@ -573,21 +573,21 @@ void svga_render_24bpp_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x += 4)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[svga->ma & svga->vram_display_mask]);
                         p[x] = dat & 0xffffff;
                         
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 3) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 3) & svga->vram_display_mask]);
                         p[x + 1] = dat & 0xffffff;
                         
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 6) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 6) & svga->vram_display_mask]);
                         p[x + 2] = dat & 0xffffff;
                         
-                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 9) & svga->vrammask]);
+                        dat = *(uint32_t *)(&svga->vram[(svga->ma + 9) & svga->vram_display_mask]);
                         p[x + 3] = dat & 0xffffff;
                         
                         svga->ma += 12;
                 }
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -608,7 +608,7 @@ void svga_render_32bpp_lowres(svga_t *svga)
                 {
                         fg = svga->vram[svga->ma] | (svga->vram[svga->ma + 1] << 8) | (svga->vram[svga->ma + 2] << 16);
                         svga->ma += 4; 
-                        svga->ma &= svga->vrammask;
+                        svga->ma &= svga->vram_display_mask;
                         ((uint32_t *)buffer32->line[svga->displine])[(x << 1) + offset] = ((uint32_t *)buffer32->line[svga->displine])[(x << 1) + 1 + offset] = fg;
                 }
         }
@@ -630,11 +630,11 @@ void svga_render_32bpp_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x++)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vram_display_mask]);
                         p[x] = dat & 0xffffff;
                 }
                 svga->ma += 4; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -652,11 +652,11 @@ void svga_render_ABGR8888_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x++)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vram_display_mask]);
                         p[x] = ((dat & 0xff0000) >> 16) | (dat & 0x00ff00) | ((dat & 0x0000ff) << 16);
                 }
                 svga->ma += 4; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
 
@@ -674,10 +674,10 @@ void svga_render_RGBA8888_highres(svga_t *svga)
 
                 for (x = 0; x <= svga->hdisp; x++)
                 {
-                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vrammask]);
+                        uint32_t dat = *(uint32_t *)(&svga->vram[(svga->ma + (x << 2)) & svga->vram_display_mask]);
                         p[x] = dat >> 8;
                 }
                 svga->ma += 4; 
-                svga->ma &= svga->vrammask;
+                svga->ma &= svga->vram_display_mask;
         }
 }
diff --git a/src/vid_tvga.c b/src/vid_tvga.c
index a5c6ae6..9d24c8b 100644
--- a/src/vid_tvga.c
+++ b/src/vid_tvga.c
@@ -128,7 +128,7 @@ void tvga_out(uint16_t addr, uint8_t val, void *p)
                 switch (svga->crtcreg)
                 {
                         case 0x1e:
-                        svga->vrammask = (val & 0x80) ? tvga->vram_mask : 0x3ffff;
+                        svga->vram_display_mask = (val & 0x80) ? tvga->vram_mask : 0x3ffff;
                         break;
                 }
                 return;