diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 0ccf74e923..60c415bc9e 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -8770,6 +8770,28 @@
       <key>Value</key>
       <integer>1</integer>
     </map>
+  <key>RenderClass0MemoryBandwidth</key>
+  <map>
+    <key>Comment</key>
+    <string>Memory bandwidth at which to default to Class 0 in gigabytes per second.  Used as basis for other classes.</string>
+    <key>Persist</key>
+    <integer>1</integer>
+    <key>Type</key>
+    <string>F32</string>
+    <key>Value</key>
+    <real>16.0</real>
+  </map>
+  <key>RenderCPUBasis</key>
+  <map>
+    <key>Comment</key>
+    <string>Reference CPU clockspeed to use to bias GPU class (in MHz).</string>
+    <key>Persist</key>
+    <integer>1</integer>
+    <key>Type</key>
+    <string>F32</string>
+    <key>Value</key>
+    <real>3000.0</real>
+  </map>
   <key>RenderComplexityColorMin</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/llfeaturemanager.cpp b/indra/newview/llfeaturemanager.cpp
index 3240f169b3..c3780e42c6 100644
--- a/indra/newview/llfeaturemanager.cpp
+++ b/indra/newview/llfeaturemanager.cpp
@@ -402,6 +402,7 @@ bool LLFeatureManager::loadGPUClass()
 {
 	if (!gSavedSettings.getBOOL("SkipBenchmark"))
 	{
+        F32 class0_gbps = gSavedSettings.getF32("RenderClass0MemoryBandwidth");
 		//get memory bandwidth from benchmark
 		F32 gbps;
 		try
@@ -418,6 +419,12 @@ bool LLFeatureManager::loadGPUClass()
 			LL_WARNS("RenderInit") << "GPU benchmark failed: " << e.what() << LL_ENDL;
 		}
 	
+        // bias by CPU speed
+        F32 cpu_basis_mhz = gSavedSettings.getF32("RenderCPUBasis");
+        F32 cpu_mhz = (F32) gSysCPU.getMHz();
+        F32 cpu_bias = llclamp(cpu_mhz / cpu_basis_mhz, 0.5f, 1.f);
+        gbps *= cpu_bias;
+
 		if (gbps < 0.f)
 		{ //couldn't bench, use GLVersion
 	#if LL_DARWIN
@@ -460,23 +467,23 @@ bool LLFeatureManager::loadGPUClass()
 		{
 			mGPUClass = GPU_CLASS_1;
 		}
-		else if (gbps <= 5.f)
+		else if (gbps <= class0_gbps)
 		{
 			mGPUClass = GPU_CLASS_0;
 		}
-		else if (gbps <= 8.f)
+		else if (gbps <= class0_gbps*2.f)
 		{
 			mGPUClass = GPU_CLASS_1;
 		}
-		else if (gbps <= 16.f)
+		else if (gbps <= class0_gbps*4.f)
 		{
 			mGPUClass = GPU_CLASS_2;
 		}
-		else if (gbps <= 40.f)
+		else if (gbps <= class0_gbps*8.f)
 		{
 			mGPUClass = GPU_CLASS_3;
 		}
-		else if (gbps <= 80.f)
+		else if (gbps <= class0_gbps*16.f)
 		{
 			mGPUClass = GPU_CLASS_4;
 		}
diff --git a/indra/newview/llglsandbox.cpp b/indra/newview/llglsandbox.cpp
index 175f1849cf..0c8e248538 100644
--- a/indra/newview/llglsandbox.cpp
+++ b/indra/newview/llglsandbox.cpp
@@ -984,6 +984,7 @@ private:
 
 //-----------------------------------------------------------------------------
 // gpu_benchmark()
+//  returns measured memory bandwidth of GPU in gigabytes per second
 //-----------------------------------------------------------------------------
 F32 gpu_benchmark()
 {