0 Replies Latest reply on Jun 18, 2011 10:05 AM by Bianchi

    Intelppm.sys seems to affect USB performances

    Bianchi

      Hi. I noticed a strange behaviour of USB 2.0 on my Lenovo Ideapad Z560 (Intel Corei5, Windows 7 64 bits).For a particular application I need high speed USB 2.0 running at least at 30 MB/s, although only for several seconds. This throughput is easily reached also by not so new laptops with Vista or Xp 32 bit. But not on my new laptop! In order to find if a particular process, service or driver could impact on the USB throughput, I tried to run usb test disabling one active process-service-driver at a time. After some (boring) tries I saw that disabling the driver intelppm.sys, USB maximum rate jumped from 26 MB/sec to 31 MB/s ! For this test I measured the throughput on external USB drive by means of free software HD-Tune. After some reading about the purpose of Intelppm and its behavoiur, I obtained the same throughput leaving intelppm.sys enabled but generating dummy load on my CPU (with software "LOAD Storm"). In particular, with Intelppm active, I can obtain good performances on USB only if my CPU load is at least 50%! Anybody Knows why?