CheckCoreOverThreshold.ps1

[CmdletBinding()]
param (
    [Parameter()]
    [int]
    $PercentCPUThreshold = 80,

    [Parameter()]
    [int]
    $DurationMilliseconds = 10000
)

$coresOverThreshold = New-Object 'System.Collections.Generic.Dictionary[string, long]'
$sw = New-Object System.Diagnostics.Stopwatch
$sw.Start()

Get-Counter "\Processor(*)\% Processor Time" -Continuous | ForEach-Object {
    $_.CounterSamples | ForEach-Object {
        if ($_.CookedValue -lt $Threshold) {
            if ($coresOverThreshold.ContainsKey($_.InstanceName)) {
                [void]$coresOverThreshold.Remove($_.InstanceName)
            }
        } else {
            if ($coresOverThreshold.ContainsKey($_.InstanceName)) {
                $coreOverThresholdDuration = $sw.ElapsedMilliseconds - $coresOverThreshold[$_.InstanceName]
                if ($coreOverThresholdDuration -gt $Duration) {
                    Write-Host "Core $($_.InstanceName) has been over $Threshold% for $coreOverThresholdDuration ms"
                }
            } else {
                [void]$coresOverThreshold.Add($_.InstanceName, $sw.ElapsedMilliseconds)
            }
        }
    }
}