Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

[gdement]

I have an Intel D915GAG board on which I have replaced 3 Nichicon HN caps. It's still behaving the same as it did before the recap:

I hook up a PSU, using both the 24-pin and 4-pin connectors. The standby LED comes on. However, when I short the pins to start the motherboard, nothing happens. The lights stay on, so it doesn't seem to be a short. I hooked up a fan and there's no twitch - just no response at all. I've tested using 3 working power supplies so far, 2 of them after the recap.

I found a Gateway page documenting the board, which says I'm using the correct pins.

There is no CMOS reset jumper on the board, so I can't have messed that up either.


I don't have an LGA775 processor, and don't really intend to buy one without any prospect of the board working. Is it possible that a CPU needs to be installed in the socket for the board to power on? I've never seen that before but maybe LGA775 is different.

[Topcat]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

They will power up without a CPU, but for obvious reasons, will not POST.

[linuxguru]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

Check the obvious stuff - including the CMOS battery. Various Intel boards, from the PIII-era onwards, won't power up without a good CMOS battery.

[bgavin]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

Hmmm.... I thought the VRM needed the cpu inserted to read the ID bits, for setting the correct voltages.

[kc8adu]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

i have seen a ton of these lately that wont power up.
the lan chip is overloading +5stby.
if you are careful you could remove it.
a bad one gets very hot.
likely caused by lightning.

[gdement]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

Thanks for the suggestions.

Hmmm.... I thought the VRM needed the cpu inserted to read the ID bits, for setting the correct voltages.

Older stuff like P3/P4/Athlon don't mind powering up without a CPU, and they have VID on them. I think without a CPU it'll just read whatever value is floating on the pins when you hit the switch.

Check the obvious stuff - including the CMOS battery. Various Intel boards, from the PIII-era onwards, won't power up without a good CMOS battery.

I checked the pins underneath the battery socket, it's showing 3.03v. I tried shorting other combinations of pins on the front panel connector but it doesn't respond. Voltage across the pins on the power switch is 3.12v when not shorted.

i have seen a ton of these lately that wont power up.
the lan chip is overloading +5stby.
if you are careful you could remove it.
a bad one gets very hot.
likely caused by lightning.

Does it get hot just sitting in standby, or would I have to forcefully power it on to detect it? At standby it's only about 30C, and other chips are all in the 28-30 range. Couldn't measure northbridge due to heatsink but the heatsink was cool.
The green LED is on - wouldn't that go out if 5vsb was overloaded? Not sure what drives it.

I poked around the ATX connector and didn't find any obvious shorts, at least not when disconnected from power.

While connected to standby power, I checked the 5Vsb pin at the connector, it showed 5.05v relative to a ground pin at the same connector.

==
Thanks again for all the suggestions. This "won't power on" thing is a failure symptom I've never been able to fix. Only exception being boards with a shorted mosfet but when that happens you get a fan twitch and the PSU turns off. This one just stares at me.

[bgavin]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

Older stuff like P3/P4/Athlon don't mind powering up without a CPU, and they have VID on them.

Yes, but the OP asked about 775 chips.

I've only tried this once or twice with a 775 board, and it will not come up without the processor in the socket. I don't have enough hands-on to state if this is a fluke, or working as designed.

It is my understanding the 775 chipset VRM requires the VID to turn on. But my understanding could very well be wrong.

[gdement]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

I've only tried this once or twice with a 775 board, and it will not come up without the processor in the socket. I don't have enough hands-on to state if this is a fluke, or working as designed.

It is my understanding the 775 chipset VRM requires the VID to turn on. But my understanding could very well be wrong.

Interesting - so you've had a 775 board that wouldn't power on without a CPU, but did so once it was installed? In that case, maybe I should try to get hold of one. Might be all that's wrong.

I should also try to find a datasheet for the VRM on this board, maybe it will say something to that effect.

Thanks for the info.

[gdement]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

From the ADP3188 datasheet:

Voltage Identification DAC Inputs.
These six pins are pulled up to an internal reference, providing a Logic 1 if left open.
[...]
Leaving all the VID pins open results in the ADP3188 going into No CPU mode, shutting off its PWM outputs and pulling the PWRGD output low.

So it's pretty clear that at least the CPU voltage regulator will shut down without a processor installed.
I'm still not sure if this means *everything* on the board will be dead, or just the CPU power. I think PWRGD in this context refers to the CPU power, not the main system power supply.

Still, it looks like getting a CPU would be worthwhile.

[chipper]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

I don't know why you want to power up the board before putting in a CPU but you might try unplugging the 24pin ATX or the 12V-4pin connector / one or the other to get your desired result. ( The front panel connections are not the same as other motherboards , and may not respond to your case connection wiring the same )

It may also be that the LG775 board pin configuration is not right to allow what you may have seen in the past with other motherboards. It could also be that the LG775 does not allow anything if the CPU is not in place because it requires both connectors to run. When I first installed my new LG775 board and new processor , the new video card / or onboard video would not work at all with just the 24pin connector only. As soon as I plugged in the 4-pin connector , up came the mobo logo and the bios post was showing on the screen.

In my opinion the LG775 socket is one of the best possible choices , but there are so many other good ones that the list is almost endless. The best thing about the LG775 Socket is that it will accept about 30 different processors , depending on what mobo you have. It's absolutely an issue to purchase and install a CPU that your mobo has been tested on and recommended by the manufacturer , as some of them are listed as not being able to run on certain types of mobo's , or some of their capabilities would not be available.

[chipper]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

There are other issues with looking at the information about 775 Socket mobo's. I have seen them described as LG775 / LGA775 & LGA775 -Socket T. This can be confusing , but they all mean the same thing as far as I know.

Also there are even CPU's which clearly show that the P4 logo will be upside down in the socket according to the arrow and small upper and lower left hand side configurations for the socket. Meanwhile the CPU's also come from China/Malaysia/ Phillipines & Costa Rica , adding yet more confusion to the Intel Processor selection process. Last but not least , some CPU's are sold in a set , out of box , made without being put into sets or boxes , and with and without heatsink and fan.

Since the LGA775 processors do not have pins on them [the motherboard does] , simply scraping the bottom of the processor could wear off the (solder like) connectors , of which there are 775. Any one of them could cause a problem if damaged or slightly misaligned. It's best to buy a processor that comes with the small snap-on backing protector (black) , which can be used later on to store it if you change processors. If it doesn't have the rear cover , and it is used , it could be worn on the back already (not likely). Plus - the metal cover is heated directly onto the heatsink , which may have worn off the original lettering and markings that show the exact model of the processor and it's origin ( IE : China ) and the other indicator numbers that specify the class of processor as well.

[chipper]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

I was looking at the Gateway information about your mobo , and it shows that the section has 6 pins , if I am not mistaken. The upper section has 3 pins. The lower 2 pins are connected to "enable" bios flashing. (Bios enabled) If pins 2&3 are connected , the bios is disabled (disabling bios flashing - or bios protected ).
The lower section - 3pins - 1&2 are for normal bios retention operation , and must be installed to run on other motherboards - if removed , no power is connected to bios. While pins 2&3 are for flashing the bios to default settings , and must be returned to the 1&2 position to operate. This is a bit confusing if there are not 6 pins there.

I would take the pin connector off of the upper section and use (lower 1&2). The way it looks - upper pin 1&2 enables nothing without another jumper. That is how my LGA775 mobo works as well. It can be protected against changing it.

[chipper]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

That's a tricky feature. Mine has 2 jumper connectors on at all times. It's also a bit weird how the sidebars explain how it works. Like it will do this if - and that if -...

[chipper]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

One more thing - the pin allocation chart there only allows for 2-pin front connector plugs - what if your case has a 3-pin connector? Never mind ... ?

Break time -

[gdement]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

I was looking at the Gateway information about your mobo , and it shows that the section has 6 pins , if I am not mistaken. The upper section has 3 pins. The lower 2 pins are connected to "enable" bios flashing. (Bios enabled) If pins 2&3 are connected , the bios is disabled (disabling bios flashing - or bios protected ).
The lower section - 3pins - 1&2 are for normal bios retention operation , and must be installed to run on other motherboards - if removed , no power is connected to bios. While pins 2&3 are for flashing the bios to default settings , and must be returned to the 1&2 position to operate. This is a bit confusing if there are not 6 pins there.

I would take the pin connector off of the upper section and use (lower 1&2). The way it looks - upper pin 1&2 enables nothing without another jumper. That is how my LGA775 mobo works as well. It can be protected against changing it.

My board doesn't have pins installed for the "CLR CMOS" feature (lower section), but the upper section "BIOS CONFIG" is there. That jumper is on 1-2 (the lower pair). I've tried it also removed and with the jumper on 2-3.
I checked the pads on the lower section and they're all open to each other. I also confirmed that the jumper on the upper section is actually shorting the pins as it should.

I don't know why you want to power up the board before putting in a CPU but

The reason I've tried starting it without a processor is because I don't have a processor. And I'm less enthusiastic about buying a CPU+hsf for a board that appears unwilling to turn on.

you might try unplugging the 24pin ATX or the 12V-4pin connector / one or the other to get your desired result. ( The front panel connections are not the same as other motherboards , and may not respond to your case connection wiring the same )

It's been hooked up with both the 24-pin and P4 connector, but I just tried it with the P4 connector unplugged and that didn't have any effect. Not sure what you mean about the panel connections being different, but I'm just shorting the power switch pins. The board isn't in a case.


Thanks for your help, chipper. But no matter what I try, the board just stares at me. It has the LED turned on like it's ready to power up, but it ignores the power switch. I think there's probably nothing left to try other than getting a CPU. I'm doubtful that it will do any good though.

[kc8adu]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

many newer boards for example the killerbee from dell gx270 power up briefly when you first apply power. iirc the riptide does this too.
they check for a valid cpu then power down.
i think you have one of those odd btx boards gateway/evilmachines uses.bestec psu failures kill them.
if it wont even spin the fans its probably dead.get a cheap celeron to use as a test chip.
if it gets killed in the line of duty its no big loss.

[Newbie2]

Re: Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)

Definitely get a cheap Prescott Celeron D 3xx series processor and a cheap LGA775 heatsink (not the newer Celeron D 4xx series processors) as a cheap test processor. No big loss if it doesn't work.