diff --git a/tinygrad/runtime/support/am/ip.py b/tinygrad/runtime/support/am/ip.py
index 73e79c9cd6..a9153218b0 100644
--- a/tinygrad/runtime/support/am/ip.py
+++ b/tinygrad/runtime/support/am/ip.py
@@ -39,7 +39,6 @@ class AM_GMC(AM_IP):
 
     # Memory controller aperture
     self.mc_base = self.fb_base + self.paddr_base
-    self.mc_end = self.mc_base + self.adev.mm.vram_size - 1
 
     # VM aperture
     self.vm_base = self.adev.mm.va_base
@@ -97,8 +96,8 @@ class AM_GMC(AM_IP):
       self.adev.reg(f"reg{ip}MC_VM_AGP_BOT").write(0xffffffffffff >> 24, inst=inst) # disable AGP
       self.adev.reg(f"reg{ip}MC_VM_AGP_TOP").write(0, inst=inst)
 
-      self.adev.reg(f"reg{ip}MC_VM_SYSTEM_APERTURE_LOW_ADDR").write(self.mc_base >> 18, inst=inst)
-      self.adev.reg(f"reg{ip}MC_VM_SYSTEM_APERTURE_HIGH_ADDR").write(self.mc_end >> 18, inst=inst)
+      self.adev.reg(f"reg{ip}MC_VM_SYSTEM_APERTURE_LOW_ADDR").write(self.fb_base >> 18, inst=inst)
+      self.adev.reg(f"reg{ip}MC_VM_SYSTEM_APERTURE_HIGH_ADDR").write(self.fb_end >> 18, inst=inst)
       self.adev.wreg_pair(f"reg{ip}MC_VM_SYSTEM_APERTURE_DEFAULT_ADDR", "_LSB", "_MSB", self.memscratch_xgmi_paddr >> 12, inst=inst)
       self.adev.wreg_pair(f"reg{ip}VM_L2_PROTECTION_FAULT_DEFAULT_ADDR", "_LO32", "_HI32", self.dummy_page_xgmi_paddr >> 12, inst=inst)