Other: Sample the machine at 1 second intervals.

Was previously 2 per second, which was a bit excessive.  This way we get 4 minutes of history recorded.

Speculator/Speculator.Core/CpuHistory.cs

@@ -21,7 +21,6 @@ namespace Speculator.Core;
 /// </summary>
 public class CpuHistory : ViewModelBase
 {
-    private const int SamplesPerSecond = 2;
     private readonly ZxFileIo m_zxFileIo;
     private const int MaxSamples = 240;
     private readonly long m_ticksPerSample;
@@ -65,7 +64,7 @@ public CpuHistory(CPU theCpu, ZxFileIo zxFileIo)
         m_zxFileIo = zxFileIo;
         TheCpu = theCpu;
         theCpu.Ticked += OnCpuTicked;
-        m_ticksPerSample = (long)(CPU.TStatesPerSecond / SamplesPerSecond); // Two samples per second.
+        m_ticksPerSample = (long)CPU.TStatesPerSecond;
         m_ticksToNextSample = m_ticksPerSample * 5; // Start 5 seconds after machine start.
         m_lastTStateCount = 0;
     }
@@ -110,9 +109,8 @@ public void RollbackByTime(int goBackSecs)
     {
         if (m_snapshots.Count == 0)
             return;
-
-        var snapshotCount = goBackSecs * SamplesPerSecond;
-        IndexToRestore = Math.Max(0, m_snapshots.Count - snapshotCount);
+
+        IndexToRestore = Math.Max(0, m_snapshots.Count - goBackSecs);
         Rollback();
     }
 }