When using Powershell Jobs, Runspaces, or Workflows, are the threads being executed on separate cores?

I would say yes if by separate cores, you mean logical cores (not physical cores). Run something like this and notice the output from “$num”. $num represents the current logical (not physical) core on which a thread is running. If this script runs on a dual core machine (with 4 logical cores), the output of $num is a 0, 1, 2, or 3. See here for a better explanation on Logical vs Physical CPU.

$sb = {    param($sbarg)$MethodDefinition = @'[DllImport("kernel32.dll", CharSet = CharSet.Unicode)]public static extern int GetCurrentProcessorNumber();'@    $Kernel32 = Add-Type -MemberDefinition $MethodDefinition -Name 'Kernel32' -Namespace 'Win32' -PassThru    0..10 | % {    $num = $Kernel32::GetCurrentProcessorNumber()     Write-Output "[$sbarg]:[$_] on '$num'"    # simulate some work that may make the cpu busy    # perhaps watch in task manager as well to see load    $result = 1; foreach ($number in 1..1000000) {$result = $result * $number};    Start-Sleep -Milliseconds 500    }}0..10 | % {    Start-Job -ScriptBlock $sb -ArgumentList $_}Get-Job# Wait for it all to completeWhile (Get-Job -State "Running"){    Write-Output "waiting..."    Start-Sleep 2}# Getting the information back from the jobsGet-Job | Receive-Job# Clean UpGet-Job | Remove-Job