diff --git a/src/video/vid_ati_mach8.c b/src/video/vid_ati_mach8.c
index 6e2798295..0c8fb6691 100644
--- a/src/video/vid_ati_mach8.c
+++ b/src/video/vid_ati_mach8.c
@@ -5223,11 +5223,11 @@ mach32_ap_writeb(uint32_t addr, uint8_t val, void *priv)
     mach_t          *mach  = (mach_t *) priv;
     svga_t          *svga  = &mach->svga;
     const ibm8514_t *dev   = (ibm8514_t *) svga->dev8514;
-    uint8_t port_dword     = (addr - mach->linear_base) & 0xfc;
+    uint8_t port_dword     = addr & 0xfc;
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && (addr < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100) {
+        if (addr & 0x100) {
             mach_log("Port WORDB Write=%04x.\n", 0x02ee + (port_dword << 8));
             mach_accel_outb(0x02ee + (addr & 1) + (port_dword << 8), val, mach);
         } else {
@@ -5238,9 +5238,9 @@ mach32_ap_writeb(uint32_t addr, uint8_t val, void *priv)
         mach_log("Linear WORDB Write=%08x, val=%02x, ON=%x, dpconfig=%04x, apsize=%08x.\n",
                  addr & dev->vram_mask, val, dev->on, mach->accel.dp_config, mach->ap_size << 20);
         if (dev->on)
-            mach32_write_common(addr - mach->linear_base, val, 1, mach, svga);
+            mach32_write_common(addr, val, 1, mach, svga);
         else
-            svga_write_linear(addr - mach->linear_base, val, svga);
+            svga_write_linear(addr, val, svga);
     }
 }
 
@@ -5250,11 +5250,11 @@ mach32_ap_writew(uint32_t addr, uint16_t val, void *priv)
     mach_t          *mach  = (mach_t *) priv;
     svga_t          *svga  = &mach->svga;
     const ibm8514_t *dev   = (ibm8514_t *) svga->dev8514;
-    uint8_t port_dword     = (addr - mach->linear_base) & 0xfc;
+    uint8_t port_dword     = addr & 0xfc;
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && ((addr - mach->linear_base) < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100) {
+        if (addr & 0x100) {
             mach_log("Port WORDW Write=%04x.\n", 0x02ee + (port_dword << 8));
             mach_accel_outw(0x02ee + (port_dword << 8), val, mach);
         } else {
@@ -5265,9 +5265,9 @@ mach32_ap_writew(uint32_t addr, uint16_t val, void *priv)
         mach_log("Linear WORDW Write=%08x, val=%04x, ON=%x, dpconfig=%04x, apsize=%08x.\n",
                  addr - mach->linear_base, val, dev->on, mach->accel.dp_config, mach->ap_size << 20);
         if (dev->on)
-            mach32_writew_linear(addr - mach->linear_base, val, mach);
+            mach32_writew_linear(addr, val, mach);
         else
-            svga_writew_linear(addr - mach->linear_base, val, svga);
+            svga_writew_linear(addr, val, svga);
     }
 }
 
@@ -5277,11 +5277,11 @@ mach32_ap_writel(uint32_t addr, uint32_t val, void *priv)
     mach_t          *mach  = (mach_t *) priv;
     svga_t          *svga  = &mach->svga;
     const ibm8514_t *dev   = (ibm8514_t *) svga->dev8514;
-    uint8_t port_dword     = (addr - mach->linear_base) & 0xfc;
+    uint8_t port_dword     = addr & 0xfc;
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && ((addr - mach->linear_base) < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100) {
+        if (addr & 0x100) {
             mach_log("Port WORDL Write=%04x.\n", 0x02ee + (port_dword << 8));
             mach_accel_outw(0x02ee + (port_dword << 8), val & 0xffff, mach);
             mach_accel_outw(0x02ee + (port_dword << 8) + 4, val >> 16, mach);
@@ -5294,9 +5294,9 @@ mach32_ap_writel(uint32_t addr, uint32_t val, void *priv)
         mach_log("Linear WORDL Write=%08x, val=%08x, ON=%x, dpconfig=%04x, apsize=%08x.\n",
                  addr - mach->linear_base, val, dev->on, mach->accel.dp_config, mach->ap_size << 20);
         if (dev->on)
-            mach32_writel_linear(addr - mach->linear_base, val, mach);
+            mach32_writel_linear(addr, val, mach);
         else
-            svga_writel_linear(addr - mach->linear_base, val, svga);
+            svga_writel_linear(addr, val, svga);
     }
 }
 
@@ -5307,19 +5307,19 @@ mach32_ap_readb(uint32_t addr, void *priv)
     svga_t          *svga  = &mach->svga;
     const ibm8514_t *dev   = (ibm8514_t *) svga->dev8514;
     uint8_t temp;
-    uint8_t port_dword     = (addr - mach->linear_base) & 0xfc;
+    uint8_t port_dword     = addr & 0xfc;
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && ((addr - mach->linear_base) < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100)
+        if (addr & 0x100)
             temp = mach_accel_inb(0x02ee + (addr & 1) + (port_dword << 8), mach);
         else
             temp = mach_accel_inb(0x02e8 + (addr & 1) + (port_dword << 8), mach);
     } else {
         if (dev->on)
-            temp = mach32_read_common(addr - mach->linear_base, 1, mach, svga);
+            temp = mach32_read_common(addr, 1, mach, svga);
         else
-            temp = svga_read_linear(addr - mach->linear_base, svga);
+            temp = svga_read_linear(addr, svga);
 
         mach_log("Linear WORDB Read=%08x, ret=%02x, fast=%d.\n", addr, temp, svga->fast);
     }
@@ -5338,15 +5338,15 @@ mach32_ap_readw(uint32_t addr, void *priv)
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && ((addr - mach->linear_base) < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100)
+        if (addr & 0x100)
             temp = mach_accel_inw(0x02ee + (port_dword << 8), mach);
         else
             temp = mach_accel_inw(0x02e8 + (port_dword << 8), mach);
     } else {
         if (dev->on)
-            temp = mach32_readw_linear(addr - mach->linear_base, mach);
+            temp = mach32_readw_linear(addr, mach);
         else
-            temp = svga_readw_linear(addr - mach->linear_base, svga);
+            temp = svga_readw_linear(addr, svga);
 
         mach_log("Linear WORDW Read=%08x, ret=%04x.\n", addr, temp);
     }
@@ -5361,11 +5361,11 @@ mach32_ap_readl(uint32_t addr, void *priv)
     svga_t          *svga  = &mach->svga;
     const ibm8514_t *dev   = (ibm8514_t *) svga->dev8514;
     uint32_t temp;
-    uint8_t port_dword     = (addr - mach->linear_base) & 0xfc;
+    uint8_t port_dword     = addr & 0xfc;
 
     if (((mach->local_cntl & 0x20) || (mach->pci_cntl_reg & 0x80)) &&
         (((addr - mach->linear_base) >= ((mach->ap_size << 20) - 0x200)) && ((addr - mach->linear_base) < (mach->ap_size << 20)))) {
-        if ((addr - mach->linear_base) & 0x100) {
+        if (addr & 0x100) {
             temp = mach_accel_inw(0x02ee + (port_dword << 8), mach);
             temp |= (mach_accel_inw(0x02ee + (port_dword << 8) + 4, mach) << 8);
         } else {
@@ -5374,9 +5374,9 @@ mach32_ap_readl(uint32_t addr, void *priv)
         }
     } else {
         if (dev->on)
-            temp = mach32_readl_linear(addr - mach->linear_base, mach);
+            temp = mach32_readl_linear(addr, mach);
         else
-            temp = svga_readl_linear(addr - mach->linear_base, svga);
+            temp = svga_readl_linear(addr, svga);
 
         mach_log("Linear WORDL Read=%08x, ret=%08x, ON%d.\n", addr, temp, dev->on);
     }