Pushing the limits of "General" - PC issues

[PetrosA]

I'm hoping there are some PC builders here that might be able to help me on this one. I recently rebuilt/upgraded my workstation after the previous mobo failed with a new ASUS P5Q SE PLUS, a Core 2 Duo E8500, WD VelociRaptor and WIN7. I kept my existing SeaSonic S12-380 380W ATX12V power supply and 3 Gigs of Corsair XMS2 memory. It's been running fine 24/7 for four weeks (built at beginning of July). Today it was sitting locked out with the login screen when  all of a sudden it shut down. Attempts to restart it didn't work from the button and only after I unplugged it and plugged it back in did it try to start. The RAM sticks have LED indicators on them like the level meters on an amplifier and they were going wacky, skipping rows, etc and after a few seconds they'd shut off as though some safety had kicked in.

It wouldn't boot at all after the shutdown and since I don't have parts to swap the mobo, PSU or GFX card, I took it in for diagnosis. do these symptoms ring any bells for anyone here? What should I be expecting to hear from the techs?

[marianoapp]

i don't know what video card do you have, but that power supply doesn't look big enough..


does it beeps with an error code while booting? [anything except a short beep is an error]

things to try
- clear the CMOS [there's usually a jumper or a button near the battery]
- unplug EVERYTHING, leave just the processor and a stick of RAM. It has to boot and beep a "video error" [beep codes]. If it works start pluging in one thing at the time and see what is the cause.
- check that the power supply is well connected to the motherboard [both cables, the 24 wires one and the 6 wires one]

[DJPhil]

Finally, a question I can definitely answer.

If you don't see any burn marks or smell any magic smoke it's a good start!

First I'd try re-seating all the easy connections (Power, HDD, memory, but not the CPU). Sometimes it's just something loose. While you're in there look for any stray screws or debris that could cause a short. I always lift up the case and give it a shake and check the back of the motherboard with a good flashlight if I can get to it without major surgery.

Next I'd test the power supply, (be very careful). You can short pin 14 to ground (any black wire) to turn on the supply when it's detached from everything else. First listen for the power supply fan, if that's not on then either it didn't work or the supply's dead. I've attached the pinout for the basic ATX 20 pin connector below, the optional connector uses the same color codes. Basically you're just looking for roughly the right voltages where they should be. I've only seen a half dead power supply once (no 12V) but it can happen. There's a pwr_ok line that should handle voltage checks, but it can fail too, and it doesn't always cover all the rails. If you're uncomfortable tinkering with the supply then feel free to skip it, it's totally understandable.

From here it's all about isolating parts. If you can borrow someone else's machine that'll allow you to swap parts out to confirm they're good. If you have no other option you can try unplugging everything from the power supply but the motherboard just to see if you can get it started. Even pulling the video card and starting the computer without it should get you a post code, assuming you have a speaker hooked up. Check the manual if you have it (if not you can probably download it) for details on post error codes. Any 8? 0.25W or so speaker can be used, so you can 'borrow' one from elsewhere if you need. Some (should be all!) manufacturers splurge on an onboard beeper to save you the trouble.

Hope that helps some

Edit: Found this in a newegg review. I've seen it before, and it's probably worth checking.

Hey all, I think I may have stumbled upon an issue which seems to affect pci boards from various manufacturers including asus.

Basic Symptom: a blank display screen, after powering up machine - regardless of being completely off (prior), or in sleep mode/state. Progressively occurring more often over time.

Possible Solution: unscrew the metal pci slot bracket (preattached to all videocards); *gently & firmly* installing the card back into place (motherboard); connect monitor; power system on/off until satisfied with results.

Contributing factors seem to be: insufficient 'cumulative' height (horizontal view on table) of a motherboard's circuit board, and or plastic pci input slots used on motherboards; and least likely - radical case design interfering with sitting height of the pci cards.

To clarify a bit, the tolerances are sloppy between case frame and pci slot heights in just about everything. If it's a lot of work to tighten down the GPU then unscrew the bracket and the socket screws so it moves loosely, snap the card in, and tighten everything back up. This removes the unnecessary pressure in the system, hopefully avoiding connection problems.

[PetrosA]

I went back to the newegg reviews and yep, lots of dead ones out there. Normally I'd sit and try and figure this out myself, but life's a little more hectic with a 2 year old in the house and a business to run Worst of all, I don't have spare parts to swap out on this machine. It's probably going to cost me a fortune just to get the diagnosis from the repair guy, but I really don't have the time to deal with it .

I don't have a speaker hooked up, so can't say whether the beeps are right or not. The PSU tested ok by the tech with one of those PSU testers. Of course, that doesn't tell me if it's functioning properly under load, but at least it's a start. My GFX card is a FireGL V3300, so not very power hungry. I haven't hooked up all of the peripherals yet, so it should have been fine with what load was on it. Now that I've had some time to do some reading, it's sounding like the board is dead. Should be fun getting that replaced...

Thanks for your answers!

[djsb]

I suspect your power supply is operating at its margins and I'd recommend you buy a new one. I'm using a corsair HX650W

http://www.corsair.com/products/hx650/default.aspx

This power supply has a 7 year warranty that Corsair stands behind 100%. The one I have installed is a new replacement (replaced under warranty) for my previous HX620W (5 year warranty) which stopped working after 3 year of use. Cost me £40 to send back to Corsair in Holland and a week and a half later a brand new supply arrived. They sent me the newer 650w model with a longer warranty as well. Great company and products.

David.

P.S Some ebay links

HX620W

http://shop.ebay.co.uk/?_from=R40&_trksid=p3907.m570.l1313&_nkw=hx620w&_sacat=See-All-Categories

HX650W

http://shop.ebay.co.uk/i.html?_nkw=hx650w&_sacat=0&_dmpt=UK_Computing_PowerSupplies_EH&_odkw=hx620w&_osacat=0&bkBtn=&_trksid=p3286.m270.l1313

[alm]

My guess would be PSU, mainboard or memory. Other parts might also be suspect, but it's easy to test without a video card (it should at least boot up and display a BIOS error that you can't see, but status indicators should be normal) or drives.

I wouldn't expect the power supply to be strained, I really doubt that that configuration comes anywhere near 380W. You really need one (or more) power-hungry high-end video cards for that. Seasonic is a good brand, so it should have no problems delivering the rated power. Of course it can break.

For example, see PC Power Consumption: How Many Watts Do We Need?. Only the top high-end gaming system (with a very power hungry dual GPU video card) under maximum load exceeds 380W, although I wouldn't recommend a 380W PSU for the #1 high-end gaming system either.

Especially on an electronics forum, I would expect people to know that 650W is way overkill for almost any 'sane' PC, although it doesn't really hurt (will be less efficient at lower power). Seasonic actually builds some of the Corsair power supplies, so it wouldn't really be a step up, more like a step sideways.

[orbiter]

If you have power to the motherboard? Try pulling all but one stick of memory out, and try each stick in memory slot 1. This can help determine if a stick has gone bad which is quite common and can cause a no boot issue.
Your PSU should be able to take the system load just fine, unless it's faulty or you have crossfired/SLi GTX295's GPU's etc.

[MTron]

Well, ill toss in my 2 cents as well... I wouldn't conclude the board is dead quite yet.

For starters unplug all unnecessary peripherals (usb, serial etc) then do as others said and pull all but 1 ram module. If it still doesn't work, rotate the ram modules to see if its just a single faulty one, and try both memory channels (denoted by different coloured slots). The fact that you said u have 3gb leads me to conclude you have 3 modules. You should defiantly consider buying a 4th, so you can run the system in a symmetrical dual channel configuration, plus more ram never hurts.

After this, if there is still no joy, unplug any internal add in cards not necessary (ie all but video card), even unplug and disconnect the HD.

Also, clarify what you mean by wont boot...does the computer power up at all? ie do case fans start turning?? If not you either have a short somewhere and the PSU is in protect mode, the header connector is not properly connected to the board, or the PSU is fried. Do what DJ phill said and short pin 14 to ground, but do it while connected to the mobo, you will need some sharp pointed shorting cable to reach in the back of the molex connector while plugged in. If the system does not power up (fans start turning) then you have a short or your psu is dead.

If the system does power on, you need to find a speaker u can connect to the MB speaker header, so u can hear the POST beeps, they can be very helpful.

I guess it also goes without saying that you should ensure all cables are fully seated and plugged in properly.


I would defiantly recommend getting a second PSU to A)test the system with first and B) even if u get a new mobo, get a new PSU, 380 is a bit punchy, likely sufficient, but i would suggest more. For a price/performance leader, the Corsair 520TX is a great power supply, Its more then you need for sure (i would say 420-450 would be ideal in your case), I personally use the 520TX on my Core2 Quad overclocked system, so it will be plenty of power, and the modular cables make tidying up the inside a breeze



***edit***

more thoughts,

if you can get into the BIOS verify the voltage to the RAM as the SPD detection of the correct voltage is usually wrong, especially with performance ram, as the MB/SPD defaults to the JEDEC 1.8v standard. For example, the OCZ Gold Edition ram i am using will be drastically undervolted by the bios. The manufacturer specifies 2.1v operating voltage which i have to manually set in the BIOS of my P5Q-E motherboard. Try manually setting yours to 1.9v (ur rams operating voltage)

[Zero999]

My guess would be PSU, mainboard or memory. Other parts might also be suspect, but it's easy to test without a video card (it should at least boot up and display a BIOS error that you can't see, but status indicators should be normal) or drives.

I wouldn't expect the power supply to be strained, I really doubt that that configuration comes anywhere near 380W. You really need one (or more) power-hungry high-end video cards for that. Seasonic is a good brand, so it should have no problems delivering the rated power. Of course it can break.

For example, see PC Power Consumption: How Many Watts Do We Need?. Only the top high-end gaming system (with a very power hungry dual GPU video card) under maximum load exceeds 380W, although I wouldn't recommend a 380W PSU for the #1 high-end gaming system either.

Especially on an electronics forum, I would expect people to know that 650W is way overkill for almost any 'sane' PC, although it doesn't really hurt (will be less efficient at lower power). Seasonic actually builds some of the Corsair power supplies, so it wouldn't really be a step up, more like a step sideways.

I would've thought a typical PSU could take a short surge before the current limiting kicks in so if you have a 200W PSU and the PC requires 250W for a couple of seconds it shouldn't be a problem.

[djsb]

Please read the attached page from the user manual

David.

[alm]

I would've thought a typical PSU could take a short surge before the current limiting kicks in so if you have a 200W PSU and the PC requires 250W for a couple of seconds it shouldn't be a problem.

Yes, high-quality power supplies can usually exceed the rated power (at least for a short while), for example this small Seasonic 300W power supply delivers about 360W until it exceeds limits. The cheap crap might not even survive half of the rated load. But I try to design with generous margins, even in worst case conditions (continuous max. load at max. ambient temp), so I wouldn't use a power supply rated for 380W for a load of max. 370W (even if it's just because I dislike fans spinning at max speed). But I wouldn't expect any problems either.

[Zad]

When it attempts to boot, do the motherboard/cpu fans settle down to a moderate speed, or run at 100%? If they run at a moderate speed then the CPU is still active and relatively "sane". If they stick at 100% then that means the watchdog timer has kicked in and the CPU isn't running for whatever reason. I had a similar problem with my (expensive) DFI Expert motherboard where it would run for a minute or so then lock up. The time gradually shortened to the point where it totally refused to start. That power supply isn't huge, but unless you are playing 3D games then it should be sufficient headroom. I think people overestimate what sort of power a PC uses at idle.

Given the number of forum postings referred to above, it sounds to me like the motherboard has a design fault and should be swapped.

[djsb]

The manual clearly states that the minimum power supply should be 400w. It is the power demanded at start up that may exceed that needed when system settles down. Unless you have a test rig that can stress the power supply beyond it's limits (on paper) theres no way of knowing what it can supply when stressed. Asus must know what they're talking about when they recommend 400 watts. Surely it's better to build in a margin of error. Ok, the 620w supply may be overkill and the 520tx may suit better. It all depends on the budget available and how the system is to be used in future. It probably isn't any cheaper to buy a 520w rather than a 620w I don't know.

David.

[Zero999]

Yes, high-quality power supplies can usually exceed the rated power (at least for a short while), for example this small Seasonic 300W power supply delivers about 360W until it exceeds limits. The cheap crap might not even survive half of the rated load. But I try to design with generous margins, even in worst case conditions (continuous max. load at max. ambient temp), so I wouldn't use a power supply rated for 380W for a load of max. 370W (even if it's just because I dislike fans spinning at max speed). But I wouldn't expect any problems either.

Whilst it's good to play it safe, cost often becomes an issue. Fair enough you probably can't go wrong with using a slightly larger PC PSU than you need because it gives you some headroom for upgrades but I wouln't apply this philosophy for all areas of design, for example imagine how thick your house wiring would need to be if it were rated for the largest possible appliance you can connect to each socket.

The same sort of thing applies to your PC, although you need to leave some extra capacity for an extra hard drive, more RAM, a faster graphics card, more USB devices etc. but don't forget it's not likely you're going to be using everything at 100% for long periods of time.

[alm]

Whilst it's good to play it safe, cost often becomes an issue. Fair enough you probably can't go wrong with using a slightly larger PC PSU than you need because it gives you some headroom for upgrades but I wouln't apply this philosophy for all areas of design, for example imagine how thick your house wiring would need to be if it were rated for the largest possible appliance you can connect to each socket.

True, but I don't calculate it based on the sum of the peak current draw of all devices (which for hard-disks would be spin-up), but based on real power usage on full load (eg. GPU/CPU maximally stressed, all hard disks busy, optical drives, ...). This is more like designing your house wiring so the washing machine, AC, fridge compressor, all lights, computer can all be on at the same time, this doesn't happen very often, but it shouldn't blow the fuse either. And the fuses/breakers used for residential mains tolerates a significant overload for a long time (don't have the curves memorized, but something like a day to blow with a 100% overload?). I wouldn't expect a computer PSU to survive a 100% overload without shutting down or overheating.

But sometimes this is just not feasible (it's unlikely that the power company could handle this kind of load for every household), and overbooking is a fact of life. But the computer components are not uncorrelated load that you can approach statistically, it's quite possible to have the CPU and GPU close to max at the same time, and not that unlikely (game that stresses both). The same game might also be reading from a DVD or hard drive, and cause fans to spin up.

The same sort of thing applies to your PC, although you need to leave some extra capacity for an extra hard drive, more RAM, a faster graphics card, more USB devices etc. but don't forget it's not likely you're going to be using everything at 100% for long periods of time.

Those extra hard drive and USB devices probably already take up that 9W that the 380W power supply had left (based on published specifications). And your average computer is usually not stressed for long times, but in my opinion, the hardware should be stable under all conditions, no matter what I throw at it (which might include being stressed for hours). Making the margins large enough to take care of exceptional circumstances helps. Maybe there is a state which draws even more power than my test? An overloaded power supply will produce noisy output and might even have rails out-of-spec, which could cause a crash and data loss. Compared to the $20 or so for slightly more power (430-530W or so for the 370W max. system), this seems an easy trade-off.

Note that my original post was to counter the myth that you need 600W+ power supplies for your average system, and that 380W was inadequate for Petros's system. That 370W system was a pretty high-end gaming system, not your average office machine. So I'm not at all an advocate for huge power supplies, and would love more high-quality 250-350W power supplies, since these are plenty for most systems without high-end video card.

[Zero999]

I see your point and agree with you about everything you've said regarding PC PSUs.

I wonder how long it would take for the fuse to blow, if I turned on all of the high powered devices in the house? I could probably work out the current and look at the curves for the circuit breakers but I probably won't bother.

[orbiter]

Whilst we're on the PSU track here (excuse the pun,) you guys may be interested in the link below for any possible PSU considerations/upgrades. It's a great little calculator and even has options to factor in all your add-ons like cold cathode tubes, water pumps, CPU overclocking etc. It can even factor in capacitor aging.

Before I build any systems I always turn to this little tool to help gauge what PSU a system may need. Although It's actually pretty easy to work out what a system will need if it doesn't have much to it and is being left as standard, but when building high end gaming systems that will be utilizing dual/tri and even quad GPU's, ordinary PSU's just don't cut the mustard and 1 - 1.5kW PSU's are the norm. I always tell people to buy the best PSU's they possibly afford when they're going for medium to high end systems as cheapo ones can, and do take out the whole system if they go wrong. Really good quality PSU's are not really that much more expensive (watt for watt) so having their built-in protection mechanisms to look after the rest of the system in the event of PSU failure is well worth it.

Only recently my whole £3500 PC was saved by this protection when a brand new Enermax 1200W PSU literally blew up internally, the sytem was running a benchmarking program with the CPU at 4.4GHz when it want BANG!. Even though the PSU fried itself, the rest of the system was fine once I fitted the new PSU, although I must admit.. I did have pretty bad heartburn for a few days whilst waiting for the new one to arrive, just hoping and praying that my pride and joy wasn't dead.

Anyway, on to the PSU calculator..

http://extreme.outervision.com/psucalculatorlite.jsp

[djsb]

Exactly the point I've been trying to get across. When my old power supply went POP I was pleased I'd spent that bit extra on one with a proper quarantee. Cant be all that good a power supply if it broke after 3 years I hear you say. However it was the first one that Corsair made and can be forgiven for not being perfect. That guarantee made all the difference.
I was worried that the mainboard had been damaged but needn't have.
Anyway nothing more to say on this topic I've had my say and it's down to the OP what they do next.

David.

[PetrosA]

Thanks for all the excellent ideas! I got a call today from the service tech and he found that the mb battery was dead, and the CMOS needed to be reset. I read about that on some of the newegg.com reviews, but since I didn't have the PC set up to sleep (which all the complaints there seemed to have in common) I didn't think it had anything to do with my issue.

That calculator link is great! My system (once I put everything back into it...) and running at 90% capacity comes to 299W which gives me about a 20% buffer so I think I should be good with my PSU for now. I was pretty sure the PSU I got back then was a pretty good one but I will look into the Corsair PSUs when I can afford an upgrade since that warranty sounds very nice. As I read the excerpt from the manual, a fully loaded mb requires a 400W PSU minimum, which to me means all six HD being used, two IDE devices, all the slots used, etc., and I'm not close to doing that.

About load calcs for homes - here in the US the basic system we use is the 80/125 system. That means that the calculated load can run continuously (more than 3 hours at a time) using 80% of the rated amperage of the circuit feeding it, so you're wiring for 125% of the load. That gives a nice margin of safety.

Ex.: if I want to put incandescent lights on a 15A 120V (nominal) circuit, I can put 1440W on safely.

There are more complicated calcs for things like motors which have high peak starting currents, but that's not really important here.

Circuit breakers - there are two kinds of tripping mechanisms; magnetic and thermal. The magnetic trip very fast for things like a dead short or heavy overloads and the thermal trips for gradual overloads. How long it takes to trip the thermal (bi-metal) depends of the quality of the breaker components, ambient temperature, how well the wire is carrying heat away from the breaker etc., but alm could theoretically be right and most breakers could carry 100% of their rated load for many hours before tripping, especially if they don't have huge peak starting currents. They will fail fast though if loaded like that for long.

Anyway, I try to maintain the 80% ratio when planning a PSU, since as someone mentioned, over-sizing lowers efficiency and I try to keep my power needs low to begin with

[alm]

http://extreme.outervision.com/psucalculatorlite.jsp

Just a warning that many PSU calculators are extremely pessimistic. For example, I entered the high-end gaming PC #2 from the review I quoted earlier. The calculator states at least a 720W PSU, the review measured 500W max, and 360W in 3DMark 06 (which is probably more similar to you typical gaming load). Not that it would hurt to get a 750W PSU for this system, but 720W is certainly not the minimum, and running a 750W PSU at <200W (light load) might not give you great efficiency.

I agree with you about get the best quality you can get, just don't confuse best quality with high power (although most high quality PSU's are 400W+).

[orbiter]

Yes I agree alm, It's always best to read reviews on a PSU's before buying too if you can. A good site to check is 'Jonny Guru' (link below.) He tests most available PSU's in many different ways, taking all sorts of measurments into account and ends up giving a good honest review of the PSU. His reviews are very highly regarded in the PC building community and I know for a fact that a lot of builders head over there first before spending a load of money on a top end PSU. It's quite surprising actually how many well known & supposed high quality PSU's dont actually perform very well at all in tests, especailly considering their price tag.    

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Review_Cat&recatnum=13

orb

[PetrosA]

Well, $83 later I'm back on my box. They changed the battery and reset the CMOS and all is well. I checked over the logs and it turns out it was set to go to sleep (although I'm pretty sure I shut that off when I set it up) and it was that sleep mode that threw it into a fit. I'll check those jumpers tomorrow and make sure they're set right. But still, it seems there's an awful lot of these mb's with bad batteries - what's up with that?!?

[ArtemisGoldfish]

Yes I agree alm, It's always best to read reviews on a PSU's before buying too if you can. A good site to check is 'Jonny Guru' (link below.) He tests most available PSU's in many different ways, taking all sorts of measurments into account and ends up giving a good honest review of the PSU. His reviews are very highly regarded in the PC building community and I know for a fact that a lot of builders head over there first before spending a load of money on a top end PSU. It's quite surprising actually how many well known & supposed high quality PSU's dont actually perform very well at all in tests, especailly considering their price tag.    

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Review_Cat&recatnum=13

orb

Oooh, I *love* that site, unlike every other site I've seen that does power supply reviews, they actually test the supplies under load. They're the reason I bought my XFX 750W supply, after my 850W Teapo (ACK!) bulged.

[orbiter]

Well, $83 later I'm back on my box. They changed the battery and reset the CMOS and all is well. I checked over the logs and it turns out it was set to go to sleep (although I'm pretty sure I shut that off when I set it up) and it was that sleep mode that threw it into a fit. I'll check those jumpers tomorrow and make sure they're set right. But still, it seems there's an awful lot of these mb's with bad batteries - what's up with that?!?

Glad your up and running again PetrosA Probably just been coincidence that the CMOS battery died when the computer went to sleep and It couldn't resume or awake properly following BIOS loss.

It's probably advisable for all of us to change our CMOS battery every few years, especially if your system spends a lot of it's time turned off, as this is when the batt is mainly used holding BIOS settings. It's certainly worth while if your system is anything other than at stock settings. I think it took me two weeks to get my 4.2Ghz overclock stable so I'd have no chance of remembering the BIOS setup for that And if you know what an Asus Rampage II Extreme BIOS looks like you'll understand why Even though the thing has 2 onboard BIOS chips and 8 different save points in each BIOS, I've still got 50 odd BIOS settings written down just in case, and even that doesn't cover memory timings which also has 25 different settings, with another 6 settings so that each module can be controllled independantly.

[alm]

Some BIOSses let you save the CMOS settings to flash, this is a useful feature for exactly this issue. From my experience, CMOS batteries don't appear to die that often, and mainly on old (5+ years) systems, so I'm not sure if replacing them every few years is necessary. What do you do to conserve CMOS settings while you replace the battery, do it while the system is turned on? I turn the system completely off (no soft-off) before replacing the battery, so the settings would be cleared anyway.

Yes, Jonnyguru, together with hardwaresecrets.com, are one of the few sites that do proper PSU reviews, taking them apart and checking component specs, plus actually loading them. Silentpcreview.com also do a decent job, but don't spend much time on parts.

[MTron]

Yes I agree alm, It's always best to read reviews on a PSU's before buying too if you can. A good site to check is 'Jonny Guru' (link below.) He tests most available PSU's in many different ways, taking all sorts of measurments into account and ends up giving a good honest review of the PSU. His reviews are very highly regarded in the PC building community and I know for a fact that a lot of builders head over there first before spending a load of money on a top end PSU. It's quite surprising actually how many well known & supposed high quality PSU's dont actually perform very well at all in tests, especailly considering their price tag.    

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Review_Cat&recatnum=13

orb

Oooh, I *love* that site, unlike every other site I've seen that does power supply reviews, they actually test the supplies under load. They're the reason I bought my XFX 750W supply, after my 850W Teapo (ACK!) bulged.

If you want reviews of that caliber also check out http://www.hardwaresecrets.com/, they not only test the PSU under its full rated load, but they also increase the load until the powersupply protection kicks in. For example, the Corsair 750HX was tested to over 900 watts before it cut out, and it was still above 80% efficiency.

http://www.hardwaresecrets.com/article/Corsair-HX750W-Power-Supply-Review/775/8

[orbiter]

Some BIOSses let you save the CMOS settings to flash, this is a useful feature for exactly this issue. From my experience, CMOS batteries don't appear to die that often, and mainly on old (5+ years) systems, so I'm not sure if replacing them every few years is necessary. What do you do to conserve CMOS settings while you replace the battery, do it while the system is turned on? I turn the system completely off (no soft-off) before replacing the battery, so the settings would be cleared anyway.

Yes, Jonnyguru, together with hardwaresecrets.com, are one of the few sites that do proper PSU reviews, taking them apart and checking component specs, plus actually loading them. Silentpcreview.com also do a decent job, but don't spend much time on parts.

Yes, Some boards just don't use batteries that quickly, even when they've been off for years. In fact I still have a couple of brand new mobo's that are around 8 year old now and the BIOS settings are the same as I left them when I set them up. I guess some boards are just designed better and manage their battery power much more efficiently.

Yes I sometimes will replace a battery whilst a system is running, you just have to be careful not to drop it or let it spring out to possibly short something. I'll normally just use a rubber sucker on the battery, or wrap a piece of sticky tape around my finger (sticky stuff on the outside) and stick it to the battery before popping it out. A lot of the time though if you prefer to switch the system off, the BIOS will hold it's settings just long enough to whip the battery out and replace it.

If you want reviews of that caliber also check out http://www.hardwaresecrets.com/, they not only test the PSU under its full rated load, but they also increase the load until the powersupply protection kicks in. For example, the Corsair 750HX was tested to over 900 watts before it cut out, and it was still above 80% efficiency.

http://www.hardwaresecrets.com/article/Corsair-HX750W-Power-Supply-Review/775/8

Yes I think I was that site that I checked a few years back when I was building systems where 750W would be plenty and the Corsair TX750's would do just fine, I even had one of those myself and it was a great PSU that would also put out 900W quite happily if required. However in recent years I've been building with Enermax PSU's, mainly the Revolution85+ 1200W as IMHO it's one of the best, and most efficient PSU's made, although there is a very good competitor now in the new Corsair 1200AX.