diff --git a/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs b/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
index bdfc331..3545015 100644
--- a/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
+++ b/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
@@ -1069,7 +1069,8 @@ internal static partial class PrimeOrderCalculator
 					// 	continue;
 					// }
 
-					bool isPrime = PrimeTester.IsPrimeInternal(composite, CancellationToken.None);
+					bool isPrime = PrimeTester.IsPrimeGpu(composite);
+					// bool isPrime = PrimeTester.IsPrimeInternal(composite, CancellationToken.None);
 					// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
 
 					if (isPrime)
@@ -1130,7 +1131,8 @@ internal static partial class PrimeOrderCalculator
 
 			if (!entry.HasKnownPrimality)
 			{
-				bool isPrime = PrimeTester.IsPrimeInternal(composite, CancellationToken.None);
+				bool isPrime = PrimeTester.IsPrimeGpu(composite);
+				// bool isPrime = PrimeTester.IsPrimeInternal(composite, CancellationToken.None);
 				// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
 				entry = entry.WithPrimality(isPrime);
 				pending[index] = entry;
@@ -1160,7 +1162,8 @@ internal static partial class PrimeOrderCalculator
 		}
 		else
 		{
-			cofactorIsPrime = PrimeTester.IsPrimeInternal(cofactor, CancellationToken.None);
+			cofactorIsPrime = PrimeTester.IsPrimeGpu(cofactor);
+			// cofactorIsPrime = PrimeTester.IsPrimeInternal(cofactor, CancellationToken.None);
 			// cofactorIsPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(cofactor);
 		}
 
@@ -1689,7 +1692,8 @@ internal static partial class PrimeOrderCalculator
 			return;
 		}
 
-		bool isPrime = PrimeTester.IsPrimeInternal(value, CancellationToken.None);
+		bool isPrime = PrimeTester.IsPrimeGpu(value);
+		// bool isPrime = PrimeTester.IsPrimeInternal(value, CancellationToken.None);
 		// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(value);
 		if (!knownComposite && isPrime)
 		{
@@ -1700,7 +1704,8 @@ internal static partial class PrimeOrderCalculator
 		ulong factor = PollardRhoStrict(value);
 		ulong quotient = value / factor;
 
-		isPrime = PrimeTester.IsPrimeInternal(factor, CancellationToken.None);
+		isPrime = PrimeTester.IsPrimeGpu(factor);
+		// isPrime = PrimeTester.IsPrimeInternal(factor, CancellationToken.None);
 		// isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factor);
 		if (isPrime)
 		{
@@ -1730,7 +1735,8 @@ internal static partial class PrimeOrderCalculator
 		}
 		else
 		{
-		isPrime = PrimeTester.IsPrimeInternal(quotient, CancellationToken.None);
+			isPrime = PrimeTester.IsPrimeGpu(quotient);
+			// isPrime = PrimeTester.IsPrimeInternal(quotient, CancellationToken.None);
 			// isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(quotient);
 		}