
après moultes mises à jour de pilotes ...
voici ce que dit HDTach sur le disque systeme


ça fonctionne "normalement", le débit est redevenu normal, mais des pointes d'utilisation cpu à >30% lors des accès de disques ... chiant la souris accroche ...Re-enable DMA using the Registry Editor
My thanks go to my fellow MVP Alexander Grigoriev who taught me this method.
Run REGEDIT. Go to the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}
It has subkeys like 0000, 0001, 0002, etc. Normally 0001 is the primary IDE channel, 0002 the secondary, but other numbers can occur under certain circumstances. You have to go through these subkeys and check the DriverDesc value until you find the proper IDE channel.
Delete MasterIdDataChecksum or SlaveIdDataChecksum, depending on whether the device in question is attached as master or slave, but it can't actually hurt to delete both. Reboot. The drive DMA capabilities will be redetected.
Open Device Manager again and check whether the device is now actually using DMA mode. If so, congratulations, you've made it (at least until the next time Windows disables DMA).