My Desktop PC hangs in the BIOS boot phase when my KVM is attached. If I unplug the USB connecting the PC to the KVM, the PC boots without hanging. If the USB of the PC is connected directly to the keyboard and mouse, it does not hang.
After contacting the KVM maker and discussing the problem on several forums, I still have no solution. So I would like to consider making my own solution.
The Desktop PC has an ASRock G31M-GS R2.0 Motherboard.The attached KVM is a Startech 4 port DVI USB KVM Switch with Audio and USB 2.0 Hub, SV431DVIUA.
I contacted the KVM maker Startech, who advised "In STANDARD CMOS, set HALT ON ERROR to ALL BUT KEYBOARD" in the "STANDARD CMOS settings" but I could not find this setting. I also discussed the problem on several forums, but did not arrive at a solution
- ASRock forum: G31M-GS R2.0: where are the STANDARD CMOS settings?
- Tom's Hardware forum: G31M-GS R2.0: where are the STANDARD CMOS settings?
- TweakTown forum: G31M-GS R2.0: where are the STANDARD CMOS settings?
I noticed that the hang at the BIOS occurs when the PC is powered up "from the cold" with the KVM attached. If I have left it plugged in for a while, it boots straight through with the KVM without hanging. If the KVM is not attached via the USB then it boots straight through in all cases.
It is a minor inconvenience but I like the idea of fixing the issue.
It seems to me to be some kind of electrical issue as to how the KVM interacts with the motherboard via the USB. Some kind of "settling down" electrically seems to happen over time for the aforementioned scenario whereby it boots straight through if the PC is booted with the KVM if they have both been plugged in to the mains for a while, with mains power on.
So, I'm envisioning making some kind of custom mini circuit board half the size of a credit card to go between the USB input on the PC and the KVM. This board will let the usual USB traffic pass in both directions, as if it wasn't there. But its specific job would be to regulate/stabilise the current/voltage from the beginning. A combination of capacitors/resistors.
What would you recommend to do this job in terms of an outline of a circuit diagram etc?