A7V bios disaster

  • Thread starter Thread starter Peter Boyce
  • Start date Start date
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Peter Boyce

Greetings,

I flashed the 1011 bios in successfully onto an old a7v board, from the
original 1004. The board had a slight problem as in I have to run the CPU
fan off the power supply using an adapter, as the mobo cpu fan connector is
dead for some unknown reason.

As I said the bios flash worked fine, rebooted, loaded default settings,
rebooted, no problems. Then I made a fatal error:/ I enabled the CPU fan
check option, forgetting that my CPU fan is now powered off the PSU and not
the mobo. So as soon as I rebooted again, all I get now is a medium length
beep, no post, and then immediate power down :(

I tried clearing the CMOS to no effect. I though this would reset the bios
back to defaults again? I took the battery out for a few mins, no effect.

Is there any other way to reset the bios to defaults or get this board
working again, without having to reprogram the bios or similar? Or am I
totally screwed until the mobo bios is replaced? TIA
 
Peter said:
Greetings,

I flashed the 1011 bios in successfully onto an old a7v board, from the
original 1004. The board had a slight problem as in I have to run the CPU
fan off the power supply using an adapter, as the mobo cpu fan connector is
dead for some unknown reason.

As I said the bios flash worked fine, rebooted, loaded default settings,
rebooted, no problems. Then I made a fatal error:/ I enabled the CPU fan
check option, forgetting that my CPU fan is now powered off the PSU and not
the mobo. So as soon as I rebooted again, all I get now is a medium length
beep, no post, and then immediate power down :(

I tried clearing the CMOS to no effect. I though this would reset the bios
back to defaults again? I took the battery out for a few mins, no effect.

Is there any other way to reset the bios to defaults or get this board
working again, without having to reprogram the bios or similar? Or am I
totally screwed until the mobo bios is replaced? TIA
Click to expand...

First of all, when you clear the CMOS by shorting the jumpers (or solder
pads) or when you unplug the battery, you should make sure that AC power
is disconnected (i.e. if your power supply doesn't have an on/off
switch, unplug the cord). Soft-off mode won't cut it because the 5VSB
line is still active and maintaining CMOS contents regarldess of the
battery's status.
Assuming you have properly cleared the CMOS you shouldn't have a problem
because the logical default setting for the FAN CHECK option is OFF.

The other thing you can try of course is to plug the CPU's fan connector
into one of the other fan connectors on the motherboard (with support
for RPM sensing of course, the chipset's fan connector might not support
RPM sensing). If the fan's wires aren't long enough, you can temporarily
unscrew the fan from the heatsink, it won't do any harm for the little
time required to enter the BIOS and alter the setting.

Regards
Nikos
 
Peter said:
Is there any other way to reset the bios to defaults or get this board
working again, without having to reprogram the bios or similar? Or am
I totally screwed until the mobo bios is replaced? TIA
Click to expand...

If CPU fan check is enabled by default, you cannot change that with a new
BIOS chip. Well, maybe the default option can be modified in the BIOS image.
Even if the CPU fan header is dead, ie it's not providing power, the fan
speed sensing is maybe intact, as this is another pin. Several PSU fans f.ex
are powered from elsewhere, but have a fan sensing output that can be
connected to a mobo fan header reading out the rpm.
If you have something like that, or another fan of any type with
rpm-sensing, you can wire it to draw power from a molex connector, but
connect the sens_wire and ground_wire to the cpu fan header.
Worth a try.
 
It does sound to me like your motherboard is failing to sense rpm from the
cpu fan and shutting down or failing to start. I suspect that the default
settings would assume a 3-wire cpu fan is in place. I have a couple of
suggestions.

1. First I would make sure I'm using a fan of at least 4000 rpms with a
three wire connector. It could be that your cpu fan header is failing to
pick up a signal from the fan or the rpms could be below the safe threshold
and causing the motherboard to shut down.
2. Even if the cpu fan header is dead, it may still be able to pick up
rotational speed of a fan. You can remove the black and red wires from the
connector and plug the remaining yellow or blue wire into the cpu fan
header. That will hopefully allow the motherboard to sense rotation from
the fan. You will still have to power the fan off the power supply and you
may have to modify or make a connector to plug into the power supply. Just
be carefull to match up the power connectors with the 12 volt power wires.

Incidentally I'm still using a classic A7V with the 1011 bios in the kids
playroom. It hasn't missed a beat in about 4 years now.
 
"Steve Murphree" said:
It does sound to me like your motherboard is failing to sense rpm from the
cpu fan and shutting down or failing to start. I suspect that the default
settings would assume a 3-wire cpu fan is in place. I have a couple of
suggestions.

1. First I would make sure I'm using a fan of at least 4000 rpms with a
three wire connector. It could be that your cpu fan header is failing to
pick up a signal from the fan or the rpms could be below the safe threshold
and causing the motherboard to shut down.
2. Even if the cpu fan header is dead, it may still be able to pick up
rotational speed of a fan. You can remove the black and red wires from the
connector and plug the remaining yellow or blue wire into the cpu fan
header. That will hopefully allow the motherboard to sense rotation from
the fan. You will still have to power the fan off the power supply and you
may have to modify or make a connector to plug into the power supply. Just
be carefull to match up the power connectors with the 12 volt power wires.

Incidentally I'm still using a classic A7V with the 1011 bios in the kids
playroom. It hasn't missed a beat in about 4 years now.
Click to expand...

One solution, is to take a spare fan, and cut the +12V wire in the
center. Connect the end still left on the fan ("A" below), to the
pin on a drive connector with a yellow wire going into it. That pin
is +12V for a disk drive, and will supply power to the fan to
spin it. Keep this connected until you can finish setting the
BIOS to "ignore" the CPU fan speed. To get the necessary connector
to steal power from a drive connector, buy a drive "Y" cable
splitter and hack it up to get a drive connector plus the yellow
wire, being careful to tape up and insulate the ends of the three
unused wires on the drive connector.

---------------------------
| |
| Spare three wire fan |
| |
| Rotation +12 GND |
---------------------------
| | |
Drive power | | |
+12V (yellow) | A |
to "A" | |
| |
Tape and | B |
insulate the | | |
"B" end | | |
| | |
| | |
Motherboard CPU FAN Header

A second solution, is to splice a wire from the rotation signal
of a working fan, and connect it to the rotation signal on
the CPU fan header. You will need to chop the end off a dead fan,
to get the necessary three pin fan connector, then identify the
rotation signal on the spare carefully, as the connector is
keyed and should only be insertable one way. The idea is, one
rotation signal from a working fan, can be sent to two fan
headers without a problem.

---------------------------
| |
| Existing three pin fan |
| |
| Rotation +12 GND |
---------------------------
| | |
| | |
+---------------------+ | |
| | | |
| x x | | |
| | | | | |
| | | | | |
Rot +12 GND Rot +12 GND

CPU Fan Header

Good luck,
Paul
 
Thanks for the suggestions everyone, however the wiring solutions are a bit
beyond me.

Nikolaos, I'm sure I'm clearing the CMOS correctly, but it's not having any
effect. I'm still getting a medium length beep and no post, and immediate
power off. I tried connecting the PSU fan to the other fan connectors on the
mobo, but none of them seem to work. I'm thinking the bios update may indeed
not have been successful afterall :( I think I am clearing the CMOS
correctly, my box does have a PSU off switch, but I have also taken out the
AC power lead as an added step. I then cross the 2 solder points with a
piece of metal (flat screwdriver) before inserting the AC lead and switching
the PSU on again. When I get contact between the 2 points, there is no power
on, I assume this is when the CMOS solder points are shorted, and CMOS is
cleared? Then I power on as normal. Is this the correct way to clear the
CMOS?
 
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