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Not MPXplay bug but USB vs. CTmouse problem (Announce)

posted by RayeR(R) Homepage, CZ, 28.07.2016, 19:36

> I do know he was able to disable the SMI pin
> when he wanted the USB BIOS to leave him alone.

Interesting, I know that it is possible to program CPU external SERR# pin routing to disable generating SMI from external sources but I don't know it can be disabled at all. I think it may be even dangerous on modern HW because SMI handles some dynamic voltage and frequency control. Second usage of SMI is for legacy HW emulation - you can programm a trigger to generate SMI when e.g. keyboard I/O port is accessed (and SMI handler then execute USB handling code for it). It's true that esp. this USB handling routines can take quite a lot of time but I think there's some limit that SMI cannot execute too long to not break the OS scheduling. I don't know exactly but this time should be much less than 1ms - this should not be so long that you could observe it by jumpy mouse movement. It may happen that due to some BUG SMI waits for some timeout that is longer than expected...

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DOS gives me freedom to unlimited HW access.

 

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