----- Original Message ----- From: "William Tan" To: Sent: Tuesday, June 19, 2001 8:43 PM Subject: Re: [OT]:Some doubt about USB device. > Sorry for asking another question.... > > So, if so motherboard support USB/keyboard (hardware-level emulation), then is > the keyboard will still taking the IRQ1 and PS/2 mouse takes IRQ12 ....??? If you are using USB keyboard and USB mouse, they will be sharing the IRQ assigned to USB controller (often 11, sometimes 9, 5, etc). If you add more USB devices, they will still be sharing the common IRQ (11 for example). If not using a PS2 mouse, most motherboards will release IRQ 12 back to the system. Some motherboards will need PS2 mouse disabled in CMOS setup. IRQ 1 will probably not be reusable. > Then, how come people said that USB device won't need IRQ? All USB devices share the same IRQ, so each new device does not need a new IRQ. > For standard PC, there are just 15 IRQs. Now, most of them are used up. For an > example, if my PC is attached with a lot of USB device (let said USB 10 > devices and 2 USB 7-port hubs ), then if not enough IRQs, then how those USB > devices talk to the PC (host)??? Only one IRQ is needed for "all" of the devices. I hope this helps you. I hope I didn't make some error and offend anyone. michael -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body