Weird Mobo Problem...

  • Thread starter Thread starter Grativo
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Grativo

I just bought a Shuttle MOBO w/ Athlon 2700+ combo. The problem is that 90% of
the time when I hit the power button, the CPU fan and the MOBO power light up,
but I don't even get a post from the mobo. It does this even when I only have
the video card hooked up. 10% of the time it does post and boot up normally,
but it erases the FSB memory in the BIOS setting, and boots up at 100 Mhz FSB
setting. However, if I get into BIOS, it go back to 166 Mhz on reboot even if
I don't do anything and just exit. Anyone knows what is causing this? I've
exchanged the MOBO and power supply from the place I bought this at, and I
switched out the memory, but it still does this...I'm totally stumped...

Grativo
 
Are you using high-performance memory by any chance, like Corsair XMS, OCZ,
Mushkin, esp. > PC3200? These high-end memory products often require more
voltage than the mobo normally provides by default, so it sometimes won't
boot. In such cases, you need to increase vDimm a little to make the system
bootable. Of course, this can be a catch-22, which is why I always keep
some cheap, generic PC2100 lying around, just in case. But this is just
speculation, it could be other things, but it's one thing to consider.

Also, is this perhaps a "mobile" Athlon processor? Is the PSU a quality
unit? What model of mobo?

Jim
 
Grativo said:
I just bought a Shuttle MOBO w/ Athlon 2700+ combo. The problem is that 90% of
the time when I hit the power button, the CPU fan and the MOBO power light up,
but I don't even get a post from the mobo. It does this even when I only have
the video card hooked up. 10% of the time it does post and boot up normally,
but it erases the FSB memory in the BIOS setting, and boots up at 100 Mhz FSB
setting. However, if I get into BIOS, it go back to 166 Mhz on reboot even if
I don't do anything and just exit. Anyone knows what is causing this? I've
exchanged the MOBO and power supply from the place I bought this at, and I
switched out the memory, but it still does this...I'm totally stumped...

Grativo
Click to expand...

What happens if you press the reset button on the computer when it
fails to boot with power being turned on? (Leave the power on for this
test) There is a lead from the power supply that is used to reset the
logic on the MB. If the pulse from the PS does not occur fast enough
the MB logic will not reset and consequently not boot the computer.
Pressing the RESET button and getting the computer to boot would tend to
indicate this is where your problem might reside.

Many MBs set the FSB back to their default values when they fail to
boot as you describe. That part of the failure is not unusual.
 
I just bought a Shuttle MOBO w/ Athlon 2700+ combo. The problem is that 90% of
the time when I hit the power button, the CPU fan and the MOBO power light up,
but I don't even get a post from the mobo. It does this even when I only have
the video card hooked up. 10% of the time it does post and boot up normally,
but it erases the FSB memory in the BIOS setting, and boots up at 100 Mhz FSB
setting. However, if I get into BIOS, it go back to 166 Mhz on reboot even if
I don't do anything and just exit. Anyone knows what is causing this? I've
exchanged the MOBO and power supply from the place I bought this at, and I
switched out the memory, but it still does this...I'm totally stumped...

Grativo
Click to expand...

Try updating the BIOS.

Which model motherboard?

If it has a memory Precharge Control setting, try disabling that.

Is the power supply a name-brand, known quality unit with adequate
capacity?
 
Are you using high-performance memory by any chance, like Corsair XMS, OCZ,
Mushkin, esp. > PC3200?
Click to expand...

I'm using a Kingston pc 2700 and generic PC2700. I don't think this is a
memory issue.
Also, is this perhaps a "mobile" Athlon processor? Is the PSU a quality
unit? What model of mobo?
Click to expand...

No, regular athlon & Shuttle AN35 mobo

Grativo
 
What happens if you press the reset button on the computer when it
fails to boot with power being turned on? (Leave the power on for this
test)
Click to expand...

I'll try this when I get home.
If the pulse from the PS does not occur fast enough
the MB logic will not reset and consequently not boot the computer.
Click to expand...

What is the solution to this problem?

Grativo
 
Grativo said:
I'll try this when I get home.




What is the solution to this problem?

Grativo
Click to expand...

For most people, it would be to buy a replacement PS or live with the
problem. I have not modified this circuit on ATX power supplies, but on
AT power supplies you could trace the PG lead and look for an R/C
circuit to modify after the comparitors. It was not unusual for the
cap's value to change enough to cause a timing problem. This is NOT
recommended for those with limited electronic knowledge.

One other thing you might explore if you have this computer on a UPS,
is plugging it (the PS) into wall and seeing if there is any
improvement. My UPS is NOT a pass through type and a lower input to the
PS if it was turned on at the same time "might" provide a similar
result. This is only a theory, but it seems to occur with my UPS. If I
defer turning on the computer until after the UPS has been on for a
couple of seconds, I see this problem less on my computer. It could be
coincidence, but it might cause the PS voltage to rise slower?
 
For most people, it would be to buy a replacement PS or live with the
problem.
Click to expand...

I've tried pushing the reset button when it fails to boot and still no go. I
really don't think it's a power supply problem because I've tried it on 3
different power supplies, and it still does this...


Grativo
 
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