Your right. I miss spoke. The USB bus is polled for low / speed devices such as mice and keyboards at 1000Hz, but this is done by the host controller or root hub. --mgross >-----Original Message----- >From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] >Sent: Friday, October 28, 2005 9:36 AM >To: Gross, Mark >Cc: Holger Macht; linux-pm@xxxxxxxxxxxxxx >Subject: RE: [linux-pm] Research on device power management > >On Fri, 28 Oct 2005, Gross, Mark wrote: > >> Also, I would be interested in USB mouse and wireless mouse effects on >> the system. I know low speed usb devices result in a PCI interrupt >> every msec, > >No they don't. Interrupts occur only when data is transferred. > >On the other hand, connecting USB devices (of any speed) causes ongoing >DMA activity, which can prevent CPUs from entering their most power-saving >states. > >Alan Stern
