motherboard GA-945GCM-S2L no post

[caspian]

Dear Technicians,

I have got a desktop motherboard with model: GA-945GCM-S2L
The problem: it does not POST and nothing on the screen.
This is old but I am working on it for practice.
I hope someone give me a tip to fix it.

I have tested it with good CPu and PSU as follows:
- all power voltages are OK throughout the board including 12v, 5v, 3.3v, USB_Vcc, DDR2 1.8v, CPU_VTT , and CPU_Vcore 1.32v.
- initial power good signal is OK.
- Resume-Reset is OK.
- All clock signals are OK.
- Both the north-bridge and the south-bridge get warm. they generate some proper signals toward KBC but I did not test all their output signals.
- the CPU gets warm too.
- The motherboard has onboard graphics. I have tested it with another graphic adapter. and there was no post.
- when there is no RAM, it properly beeps.

When I plug in a RAM and turn the computer on, this happens:
clock is inserted on the BIOS IC and then some data are being read from the BIOS IC.
I see the data transfer by seeing changing voltages on the output pin of the BIOS IC.
but then the motherboard stops working and there is no beep.

Now please help me to identify which one of the followings may be the problem and how to do more tests on them:
1. BIOS is corrupted.
- it may be OK because it beeps when there is no RAM.
2. The north/south bridge is faulty.
- they may be OK because they generate some proper signals?
3. The RAM is faulty.
4. Another chip is faulty that I don't know.

[piernov]

Re: motherboard GA-945GCM-S2L no post

It would help to have a POST card.
1. You can dump the current BIOS and compare with the one from Gigabyte (hoping you have the same version), or flash their BIOS
2. If everything else is fine I think this is the last possibility
3. Well you should try with a known good RAM stick. Also sometimes you can have some incompatibilities between RAM sticks and motherboards, so you should check with several different characteristics. If you have a POST card, it should hang on a code related to RAM (depending on the kind of BIOS this motherboard has).
4. Check if anything gets hot on the motherboard. Like Ethernet or audio IC.

Also make sure you use a supported and working CPU, check the compatibility list on Gigabyte's website.

I've had a few cases like this, this is the issues I found:
— Corrupt BIOS (probably from a bad flash)
— Burnt trace on the backside of the motherboard, between RAM slot and PSU connector
— Bad contact in CPU socket (cleaned with some contact cleaner, but I guess the balls themselves are a beat weak, it's very sensitive)
— Bad contact in RAM slots (most of the times contact cleaner will do the job, but on one motherboard I had to resolder all the pins on the backside of the motherboard, after the computer had been dropped)
— Bad capacitors, especially the CPU ones and northbridge one.
— Missing components on the back of the northbridge (ceramic capacitors)

I also had a few others I couldn't fix:
— Completely burnt Ethernet chip, which probably got to the southbridge too (I will try to replace it one day)
— One wouldn't boot unless I disabled the Management Engine (you could do that on some of the firsts motherboard with ME), and after that the BIOS was rebooting randomly and acting up. Finally it would not turn on anymore, so I guess dead PCH.
— Damaged northbridge die due to the heatsink
— Some others for which I don't have any clue, so I guess bad northbridge/southbridge/PCH.

[caspian]

Re: motherboard GA-945GCM-S2L no post

thanks piernov

nothing gets hot on the board.
since data is read from the BIOS IC at the beginning, does it mean the north/south bridge are working fine?

[piernov]

Re: motherboard GA-945GCM-S2L no post

No, they can still be half-dead. Think of it as a GPU failure. The machine can still boot, but their are artifacts on the screen, sometimes it is even completely fucked up, or it crashes under load, etc… The chip still works to some extent because something is displayed on the screen, but in fact it is dead.
Since the GPU only manages the display, the only failure you'll see are related to display.
However a northbridge/southbridge does much more than that, and sometimes some parts of it work while others don't. For example you can fry the USB controller, so the USB devices are not detected anymore (or showing errors), but the rest of the system works fine.

[caspian]

Re: motherboard GA-945GCM-S2L no post

what signal should I check to ensure that the north bridge (PCH) is no problem for the motherboard to POST?

[piernov]

Re: motherboard GA-945GCM-S2L no post

I've got no idea, I don't think there is any way to determine if the northbridge is at fault, espacially when the BIOS starts to boot up… Except replacing it of course.
You should still monitor the voltages for CPU, northbridge, southbrige and RAM to see if any fluctuates due to bad capacitors or bad regulation.
You could also try to boot while pressing on the CPU, northbridge or southbridge to see if it's a solder ball issue (although it's rare, it can happen).
Also the POST card can help you know at which stage the POST fails.

[stj]

Re: motherboard GA-945GCM-S2L no post

is the bios in a socket?

[caspian]

Re: motherboard GA-945GCM-S2L no post

is the bios in a socket?

no, the BIOS is in a sop-8 flash IC.

[ala_borbe]

Re: motherboard GA-945GCM-S2L no post

best way to troubleshoot desktop board is to put known good cpu and known good psu and tun it on
if it beeps should be easy to repair
if not try diagnostic post card, they are cheap and on most of them you can see standby or working voltages present
if all are there it may be bios (gigabyte asrock biostar j&w and most board vith VIA chipset have bios isssues for not posting)
and a must try repair is to remove sound and lan IC... thay often go bad or short cosing machine not to post
but it will post without it
also check for swollen capacitors ot leaked ones
on intel board small capacitors under heatsink go bad due to heat but sometimes thay look ok. must replace them with known good, since thay may result in non post or unstable system

hope it helps

[piernov]

Re: motherboard GA-945GCM-S2L no post

— One wouldn't boot unless I disabled the Management Engine (you could do that on some of the firsts motherboard with ME), and after that the BIOS was rebooting randomly and acting up. Finally it would not turn on anymore, so I guess dead PCH.

Off-topic but I may as well report back on this one: H57D01 from Acer Aspire X3900.
PCH replaced and now it works.
At first it was acting funny, I had to play a bit with the PCH_ME_ENABLE jumper as well as power cycle a few times the board and clear CMOS. I guess it was due to the old ME region.

EDIT: Won't PXE boot with ME enabled, it can't find the DHCP server, while it works perfectly fine with ME disabled.

[esmo]

Re: motherboard GA-945GCM-S2L no post

try changing mosfets supplying north bridge.

[caspian]

Re: motherboard GA-945GCM-S2L no post

I think I should do a more comprehensive testing on this board and report back.

I discovered that CPU-Vcore Mosfets get warm (not very hot) when the board is On. The backside of the board under those Mosfets got brown by years whereas the board is blue. But the CPU-Vcore voltage is stable at 1.32v for this CPU and does not seem to have any problem.

Nothing else get hot on the board.
I think Mosfets are typical to get warm and make the board brown.

[piernov]

Re: motherboard GA-945GCM-S2L no post

MOSFETs from CPU VRM getting hot is normal especially on P4/early C2D motherboards in my experience, if you get a stable VCore this is perfectly fine.

[caspian]

Re: motherboard GA-945GCM-S2L no post

that is right, CPU_Vcore is stable.
using only multimeter, it shows that the line is stable at 1.321 volts.

[Mr.Amin]

Re: motherboard GA-945GCM-S2L no post

Hi
I Need Asrock 945GCM-S Rev:1 BIOS file flash .
Pleaze

[caspian]

Re: motherboard GA-945GCM-S2L no post

I don't have it for Asrock .
search the net.
it may be found if you search enough.

[piernov]

Re: motherboard GA-945GCM-S2L no post

Download it on Asrock website, you should be able to flash it directly.

https://www.asrock.com/MB/Intel/945GCM-S/index.asp#BIOS