[Groucho2004]

Originally Posted by manolito

Not on my ancient WinXP machine...

I used basically the same script as your "hard.avs" with a 720p clip and here are the results with my i5:

AviSynth 2.61, build:May 17 2016 [16:06:18] VC2008Exp

FPS (min | max | average):      18.57 | 198864 | 46.70
Process memory usage (max):     592 MiB
Thread count:                   13
CPU usage (average):            24.9%

AviSynth+ 0.1 (r2772, MT, i386)

FPS (min | max | average):      18.64 | 137675 | 46.88
Process memory usage (max):     142 MiB
Thread count:                   20
CPU usage (average):            24.6%

Edit: I just remembered that Avisynth (classic, not sure about AVS+) sets "SetMemoryMax()" according to the available memory:

    MEMORYSTATUS memstatus;
    GlobalMemoryStatus(&memstatus);
    // Minimum 16MB
    // else physical memory/4
    // Maximum 0.5GB
    if (memstatus.dwAvailPhys    > 64*1024*1024)
      memory_max = (__int64)memstatus.dwAvailPhys >> 2;
    else
      memory_max = 16*1024*1024;

    if (memory_max <= 0 || memory_max > 512*1024*1024) // More than 0.5GB
      memory_max = 512*1024*1024;

In your case this is probably 128 MiB. That would explain the rather moderate memory usage of Avisynth 2.6.1 in your test.