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13-11-2001, 04:25 PM
Friend sends machine from Wellington to fix problem with online stuff. Booted machine a few times while turning normal crap off to get ready to go online and suss problem. The last time I rebooted detected videocard alright,posted fine, detect CPU alright, ram test fine, plug and play detection of drives alright then....cursor moves from under last drive to next line onscreen and then the whole thing hangs. Startup disk useless. ResetCMOS useless. Strip machine to basics useless. load BIOS defaults useless. (not necessarily in that order). As I cannot get at A:/ drive cannot do anything more. All drives working in other machines fine. So am I looking at some sort of BIOS failure or could it be CPU related? Any ideas? Getting just a little frustrated I can tell you! I have done all the normal sort of things that I can think of to fix but maybe I missed something.

13-11-2001, 04:57 PM
You say you have set BIOS defaults : does this mean that it is displaying on the screen?
Check all the cables. Starting at the mains power cord. '... sends machine from Wellington' means it has been vibrated. Look for things shaken off. Turn the box over and shake and see if anything falls out.
Check any jumpers on the main board.
Reseat the memory.
Just all the silly simple things before you look for subtle failure modes.

13-11-2001, 06:26 PM
Thanks for the quick response Graham. Yes I can get to the BIOS fine. I removed everything and reseated installed just the basics. All ram is detected properly and has been tried on its own. Whats strange to me is that I was able to boot it when it first arrived and a few times at that and then it suddenly failed. However while I was rebuilding it I had occasion to shake it out (I had dropped a screw in) and lo and behold a 3 inch nail dropped out. I wonder if in all the mucking around when I first got it may have shifted the nail and shorted something. The whole boot process is totally normal till just after the drives are detected and then it hangs solid. The only error message I got was when I reset the CMOS and then I had a CMOS checksum error which the BIOS auto fixed by loading defaults and then I never saw the message again. If i could just get to my A:/ drive I would be fine but I have never experienced this type of problem before so have run into a brick wall as such.

13-11-2001, 07:23 PM
Hi John,

If you are going to talk about turning machines upside down and shaking them to see if anything falls out, please whisper so people don't think this is a normal part of a technicians repair routine :)
We all know what happens to HDDs that get a good shake.

Anyway,

It sounds to me as if you have a power supply problem. You don't say what your machines specs are but the following is especially true for newer hi spec AMDs with poor quality, low spec power supplies.


It's one possibility anyway. You should bear in mind that this is not a definitive response to your problem, as I cannot inspect your computer. There are many possible reasons why your computer has these symptoms. MY SUGGESTION IS ONLY ONE, although a good place to start nevertheless.

Each power supply completes internal checks and tests before allowing the system to start. If the test is successful, the power supply unit (PSU) sends a special signal to the motherboard called a Power_Good (Power_OK or POK). If this signal is not continuously present, the computer does not run. Therefore, when the AC voltage dips and the power supply becomes over-stressed or overheated, the Power_Good signal goes down and forces a system reset or complete shutdown. If in addition your system has been suffering from system locks (sometimes attributed to software bugs which can be the case but it can also be related to PSU problems) then this adds cumulative evidence, implicating the PSU. As you did not replace your PSU, you may have experienced the following.

On powering on your system, it may seem dead but the fan(s) and hard disk drive(s) (HDDs) are running. This is an example of a Power_Good, or should I say a Power_Not_So_Good signal. This can be confirmed by conducting the following test. If your computer fails to boot up properly the first time you turn it on via the power switch but it subsequently boots up if you use the rest button or Ctrl-Alt-Del warm boot command, then in all probability, there is a problem with the Power_Good timing and hence PSU.

Alternatively, configuring your system with the bare minimum components installed which gives no problems over a reasonable period of time?PSU is the bad guy, maybe. I say 'PSU maybe' to ward off any accusations to the possibility of it being something else - although I have said this,

The PSU powers the computer so it can operate, obviously, but it also ensures that the system does not run unless the power supplied is sufficient to operate the system properly. In short, the PSU actually prevents the computer from starting up or operating until all the correct power levels are present. The Power_Good signal is a +5V signal (with variations from +3.0 through +6.0) generated in the power supply when it has passed its internal self-tests and the output has stabilised (between 0.1 to 0.5 seconds after the power to the computer is switched on) the PSU sends the signal to the motherboard, where it is received by the processor timer chip, which controls the reset line to the processor. In the absence of Power_Good, the timer chip continually resets the processor, which prevents the system from running under bad or unstable power conditions. When the timer chip receives the Power_Good signal, it stops resetting the processor, and the processor begins executing whatever code is at address FFFF:0000 (usually the ROM BIOS). If the PSU cannot maintain proper outputs (such as when burnout's occur), the Power_Good signal is withdrawn, and the processor is automatically reset. When the power output returns to its proper levels, the PSU regenerates the Power_Good signal and the system again begins operating (as if it is had been powered on). A resetting computer indicates a Power_Good abortive action and leading one to suspect a PSU problem. By withdrawing the Power_Good signal, the system should never use an erratic energy supply because it is stopped quickly (reset) rather than being allowed to operate using unstable or improper power levels. These power states or conditions can cause memory parity errors that vary from reset to reset (sometimes misdiagnosed as a memory problem but in fact a PSU problem), CMOS memory corruption and so on. These problems can be hard to pinpoint and misdiagnosis is common.

If your computer was supplied with a cheap PSU, and this may be the case, Some motherboards are more sensitive to an improperly designed or improperly functioning Power_Good signal than others. Intermittent start-up problems like the ones you are experiencing are often the result of improper Power_Good signal timing. If you have installed additional devices, or upgraded your motherboard which is particularly sensitive to an improper Power_Good signal (not the motherboard at fault but its sensitivity is more apparent to this over-stressed PSU stated) then PSU seems at fault in some way. If the PSU is marginalised (over stressed or over heated) or poorly engineered then replacing it with a high-quality PSU instead can easily rectify a PSU problem. Have a look at PCPower & Cooling at www.pcpowerandcooling.com

PSUs often do not fail completely all at once; they can fail in an intermittent manner or allow fluctuating power levels to reach the system, which results in unstable operation (ah!) and damaged components. Does this sound familiar? You may be experiencing the following without knowing its cause. If not, then you might experience the problems listed below unless you rectify the PSU right away if it is the cause. Obviously, components do not work in isolation so any different component configuration could be causing your computer problems. To solve it will be more difficult. Therefore, isolating the PSU, RAM and so forth are worthy starting points.

Your computer system is powered by your PSU (electrical energy being the lifeblood of your computer system). Do not jeopardise the integrity of your data and the remaining computer components on a marginalised or defective PSU. Act now, and everything should work out ok.

Symptoms you are, or may experience, pertaining to a PSU problem are as follows:

? Any power-on or system start-up failures or lockups.
? Spontaneous rebooting or intermittent lockups during normal operation.
? Intermittent parity check or other memory-type errors.
? HDD and fan simultaneously failing to spin (no + 12V) (is this your systems symptoms too)
? Overheating due to fan failure.
? Small brownouts cause the system to reset.
? Electric shock felt on the case or connector
? Slight static discharges disrupt system operation.
? Removing devices eliminates problem.

The power supply is one of the most important components in your PC. Do yourself a favour and buy a new high-quality replacement if your system does not have one already.

Considering many of the problematic components have already been looked at, assuming that additional problems have not now been introduced, the PSU seems a good starting point for your investigation.

Or to put it basically your power supply could be buggered, try another one.

I hope this is of help to you. Let me know how you get on.

BC.

13-11-2001, 07:56 PM
BC's Reply - wow!!
Such a comprehensive reply deserves congratulations.

13-11-2001, 08:00 PM
Excellent BC. Thats the sort of answer I love to see. One where you learn and its relatively easy to understand. Thanks for that.

However no go. The power supply in it was brand new (I had the guy replace it not long ago) and even though its not one I would have used (he had a shop replace it ands its cheap and nasty to say the least) its alright. I happened to have a spare high quality power supply lying around (I have seen a bit of power supply related problems before)so I whacked that in. Exactly the same hang at the same point unfortunately. Still it was a great answer and thanks for that. Thats what I love about the net. You can actually learn something new and interesting everyday.

13-11-2001, 08:21 PM
Damn,

After all that I was really hoping your power supply was screwed. (not that I wish bad things upon you)
The trouble is it could be one simple problem or a combination of several things and it is going to be one of those long drawn out one by one elimination diagnosis.

One thing for sure a stray 3' nail floating around inside your case can't be good.

Best of luck to you.
BC

Try this one, my dad bought a new computer last May, A real beauty, $5000.00 worth using all good quality gear. Since then it has had 4 new motherboards! 2 lots of ram replaced, a new HDD, and the Video capture card replaced twice.
And believe it or not all 4 motherboards were confirmed as being faulty by the manufacturer, how much bad luck can one guy have!

15-11-2001, 10:02 AM
Dammit its the motherboard. All I can think is that the 3inch nail shifted when I was first moving it around and shorted the board in some way. It was a piece of crap board anyway but that did not help when it came to explaining myself to my friend. Its not easy telling somebody you have no idea what actually went wrong but you have to spend a lot of money replacing parts when all they sent it to you to fix was an online problem. I still have that to fix once I rebuild as well and I am not looking forward to that as Internet Explorer is so heavily integrated into the OS it is often very difficult to fix once its been trashed. Oh well. Thanks to all who threw ideas at me.