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Suddenly no keyboard input in Bios

Last response: in Motherboards
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April 23, 2012 2:38:56 PM

Hello,

My computer worked perfectly fine for about 2 years.
I uses an AMD2+ on a Asus M4N78 Pro main board.
But recently I wrecked the configuration of the linux boot loader on HDD and needed to enter BIOS for reconfigure the boot device.

The BIOS does not recognize any keypress, the boot loader (working with BIOS keyboard input) does neither.
I tried different Keyboards (PS2, 2 different USB) all of them used to work before, now nothing works at all.
Interestingly the POST Messages tell me that the USB devices are recognized by BIOS, but still pressing DELETE does not bring up the BIOS Screen.
I also cleared the CMOS but this didn't help.

Apart from this the machine worked well all the time, I used BIOS configuration with one of the USB keyboards some months ago. But now it is essentially bricked.
April 23, 2012 3:22:57 PM

seems to be an issue with the keyboard controller,ps2 port or maybe even the southbridge chip on ur motherboard. do the keyboard led's blink atleast twice before u see the bios screen or boot screen?
April 23, 2012 3:28:59 PM

As I said: the BIOS recognizes connected USB Keyboards correctly, and reports if I connected one or two of them.

On the PS2 KB I get the 2 LED blinks for Power on and Init, but still nothing works.
And of course, the keyboards work on other computers and are connected to the
correct ports.
Related resources
a b Ĉ ASUS
a c 156 V Motherboard
April 23, 2012 3:36:50 PM

Could also be the power supply.

The small, 5 volt AuxPS inside the PSU generally powers the PS2 ports and some or all of the USB ports.

Use a multimeter to check between the violet wire and a black wire (ground). As long as the PSU is switched on by the PSU switch, you should read 5 volts. You can carefully measure from the back of the main power plug while it is plugged into the motherboard.
April 24, 2012 8:26:19 AM

with bare motherboard, cpu ,known good p.s, one mem stick(known good) ,internal video if present boot and see if u can enter bios. if u cannot do so even with this minmum configuration(no hard disk no cd/dvd drive, no internal cards), i am afraid u have motherboard hardware issue. as a last resort u may swap with known good compatible cpu.if no integrated video then check with known good video card.
!