Hi, David,
Thank you so much for your response.
I am not quite understand what you mean by "It's safe to leave that BIOS feature enabled, unless your BIOS is buggy in that area, since Linux turns it off later if you start up the "native" USB.".
Linux should know how to kick the BIOS off, and AFAIK it does that correctly in all cases with OHCI and EHCI controllers.
On the other hand, turn it off if you like. One board's BIOS config docs say the feature is for when you "use a usb keyboard or mouse with an operating system that does not ... have any USB drivers instealled, such as DOS and SCO Unix".
So Linux clearly shouldn't care how the feature is set. But BIOS bugs do exist, and sometimes even Linux bugs.
Does "native usb" mean the usb driver in linux kernel? If it does, then USB Emulation might not be turned off even when usb drivers have started up. Because I am using RTAI, an real time abstract interface. Its latency test program shows that usb emulation causes large latency.
Well, if you isolate some performance problem in a Linux HCD, feel free to write it up and send it along.
- Dave
Thanks again,
jing
Quoting David Brownell <[EMAIL PROTECTED]>:
| What is USB emulation?
USB emulation is a BIOS option (in some BIOSen) which makes a USB keyboard and mouse look like a PS/2 keyboard and mouse. It is for use when you don't have any USB support in an OS, or won't be booting an OS.
Or when you'll be using a USB keyboard when booting, maybe to talk with the BIOS ...
It's safe to leave that BIOS feature enabled, unless your BIOS is buggy in that area, since Linux turns it off later if you start up the "native" USB.
- Dave
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