ATX mainboard question

[Sam Goldwasser]

Would NOT having memory or any peripherals plugged in prevent
an ATX power supply from turning on? I'm not referring to an
SMPS loading issue but an actual logic lockout. I can force the
power supply on by grounding the PWR-ON (green) wire but the
tower case power button has no effect. It is receiving some
voltage and does ground the power-on pin on the mainboard (which
is of course NOT directly connected to PWR-ON of the power
supply) when depressed but has absolutely no effect.

It's from a Compaq mini-tower.

The story I got was that this started when a new video card
was plugged in, possibly askew. However, that story is
somewhat jumbled so I don't have a lot of confidence in it.

Is the computer likely to boot and run properly "hot wired"
or is there some reset/initialization that really requires
the proper power on sequence?

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[Dave D]

Would NOT having memory or any peripherals plugged in prevent
an ATX power supply from turning on? I'm not referring to an
SMPS loading issue but an actual logic lockout. I can force the
power supply on by grounding the PWR-ON (green) wire but the
tower case power button has no effect. It is receiving some
voltage and does ground the power-on pin on the mainboard (which
is of course NOT directly connected to PWR-ON of the power
supply) when depressed but has absolutely no effect.

It's from a Compaq mini-tower.

The story I got was that this started when a new video card
was plugged in, possibly askew. However, that story is
somewhat jumbled so I don't have a lot of confidence in it.

Is the computer likely to boot and run properly "hot wired"
or is there some reset/initialization that really requires
the proper power on sequence?

Try clearing the CMOS Sam, I've lost count of the number of times I've
encountered apparently 'dead' boards after installing or removing PCI/AGP
peripherals. I've also encountered mobos which won't power up with dead CMOS
batteries. Does the mobo actually work when you force the power on?

Dave

 

[BOB URZ]

Would NOT having memory or any peripherals plugged in prevent
an ATX power supply from turning on? I'm not referring to an
SMPS loading issue but an actual logic lockout. I can force the
power supply on by grounding the PWR-ON (green) wire but the
tower case power button has no effect. It is receiving some
voltage and does ground the power-on pin on the mainboard (which
is of course NOT directly connected to PWR-ON of the power
supply) when depressed but has absolutely no effect.

It's from a Compaq mini-tower.

The story I got was that this started when a new video card
was plugged in, possibly askew. However, that story is
somewhat jumbled so I don't have a lot of confidence in it.

Is the computer likely to boot and run properly "hot wired"
or is there some reset/initialization that really requires
the proper power on sequence?

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
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I had a compac the other day i was working on that was dead. Swapped the
PS, no change. thought for sure it was the MB. Got a OEM MB off of ebay
(SD-11 or such original spare). put it in and it was still dead. WTF?
Turned out the video card (AGP) and modem card were shorted or such
and causing the board NOT to start up. I swapped in different cards, and all
was well. I then tested the old MB, and it started up now and ran.
The memory was OK.

BOB

So the moral of the story, bad or shorted plug in cards can cause a no
start situation.

BOB

 

[Jason D.]

This is usually made by Mitac. Junkie.

Try clearing the CMOS Sam, I've lost count of the number of times I've
encountered apparently 'dead' boards after installing or removing PCI/AGP
peripherals. I've also encountered mobos which won't power up with dead CMOS
batteries. Does the mobo actually work when you force the power on?

Dave

Even with CMOS battery in peecees, usually not a big problem for the
power control. The power management is with multi i/o stuff,
keyboard/mouse PS/2 ports controller intergrated into one 100 pin IC.
IC is powered by 5Vsb from the ATX PSU. Fixed a dead motherboard (Asus
P2B) this way by swapping that IC from another board. Check the IC
markings for compatiable swap, last few numbers is version numbers.

USB and cmos battery is routed to the southbridge.

Oh, you can do a power on test without cpu, memory with that power
button attached. Then CPU and listen for beeps, almost always does
this bec of no ram and no video. Push power button and hold 4 sec to
turn off.

That IC also allows option (set in bios settings) to use keyboard to
turn on computer.

Cheers,

Wizard

 

[Sam Goldwasser]

Try clearing the CMOS Sam, I've lost count of the number of times I've
encountered apparently 'dead' boards after installing or removing PCI/AGP
peripherals. I've also encountered mobos which won't power up with dead CMOS
batteries. Does the mobo actually work when you force the power on?

That's what I need to check next but will have to wait until I can
snag a memory card to put in it.

Thanks.

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[Sam Goldwasser]

The PC is a Compaq Presario, proabably one of the 7400 series though I
can't find a model number anywhere. The mainboard configuration and
jumper options seem to match.

So, I cleared the CMOS and installed a 256 MB DIMM.

Now it powers up and down fine. When powred on, or RESET, it goes through
the memory test. At 120 MB, the screen gets totally hosed and it hangs there.
The only key on the KB that has any effect is F9 which causes it to
terminate the memory test with "248 MB OK" (before it gest to 120 MB,
after it's ignored), move the FDD heads once or twice, then hang. No
amount of random key hitting has any effect (other than that F9).

According to

http://h18000.www1.hp.com/support/FAQs/desktops.html
(and the 7400 maintenance and troubleshooting guide),
F10 should start SETUP but F10 has absolutely no effect
at any time.

As far as I can tell, the jumpers for CPU clock multiplier, bus speed,
and core power are set correctly based on the label on the CPU chip.

What am I overlooking? Or is the BIOS corrupted or something more serious?

Thanks to all.

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[Dave D]

The PC is a Compaq Presario, proabably one of the 7400 series though I
can't find a model number anywhere. The mainboard configuration and
jumper options seem to match.

So, I cleared the CMOS and installed a 256 MB DIMM.

Now it powers up and down fine. When powred on, or RESET, it goes through
the memory test. At 120 MB, the screen gets totally hosed and it hangs there.
The only key on the KB that has any effect is F9 which causes it to
terminate the memory test with "248 MB OK" (before it gest to 120 MB,
after it's ignored), move the FDD heads once or twice, then hang. No
amount of random key hitting has any effect (other than that F9).

According to

http://h18000.www1.hp.com/support/FAQs/desktops.html
(and the 7400 maintenance and troubleshooting guide),
F10 should start SETUP but F10 has absolutely no effect
at any time.

As far as I can tell, the jumpers for CPU clock multiplier, bus speed,
and core power are set correctly based on the label on the CPU chip.

What am I overlooking? Or is the BIOS corrupted or something more serious?

Thanks to all.

A long shot- is the memory fast enough for the CPU bus speed? installing a
PC100 Dimm where a PC133 is required, or a PC66 where PC100 is required can
cause these symptoms. Some systems don't even like it when *faster* memory
is used, though usually that is laptops.

Failing that, it could be bad memory or, quite simply, a buggered
motherboard. You could try altering the memory settings in the CMOS (the CL
rating) if it provides that facility, (not bloody likely with Compaq!) but
it is a long shot.

Dave

 

[Dave D]

So, I cleared the CMOS and installed a 256 MB DIMM.

It just occured to me, the motherboard might not support this configuration.
It might work with only single sided 256MB, only double sided 256MB etc. The
reason I mention this is that it counts almost half the Dimm then fails.
It's only a hunch but it's worth checking out.

Dave

 

[Sam Goldwasser]

It just occured to me, the motherboard might not support this configuration.
It might work with only single sided 256MB, only double sided 256MB etc. The
reason I mention this is that it counts almost half the Dimm then fails.
It's only a hunch but it's worth checking out.

Both your suggestions may have validity. The memory is a PC133 and the
bus is I guess 97 MHz.

I'll see what other memory I can find as well as checking the specs
of the mainboard.

Thanks.

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[none]

It just occured to me, the motherboard might not support this configuration.
It might work with only single sided 256MB, only double sided 256MB etc. The
reason I mention this is that it counts almost half the Dimm then fails.
It's only a hunch but it's worth checking out.

Correct. The Intel BX does not support single sided 256MB DIMMS. There are
probably other chipsets that won't work as well.

 

[Laurence Payne]

The PC is a Compaq Presario, proabably one of the 7400 series though I

can't find a model number anywhere. The mainboard configuration and
jumper options seem to match.

Compaq. That one word makes me reluctant to continue.
Look up the cost of a new ATX motherboard suitable for whatever CPU
you have. When you've finished being surprised how cheap it is, buy
one and set up again free of Compaq's non-standard annoyances.

 

[Dave D]

I'm not sure why I'm spending so much time on this though.

I do stuff like that. I can't explain why I do it, it's just addictive I
suppose

Dave

 

[Sam Goldwasser]

Compaq. That one word makes me reluctant to continue.
Look up the cost of a new ATX motherboard suitable for whatever CPU
you have. When you've finished being surprised how cheap it is, buy
one and set up again free of Compaq's non-standard annoyances.

Well, Win98 is running fine on it now. The only remaining issue is to
find the proper driver for the on-board video. It looks like I can download
it from the Compaq Web site.

Sorry, I agree with you about Compaq. But I'm not doing this because I
need another PC. Just can't stand to see it go to waste. And, so
far, I really haven't seen that much to complain about.

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