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#11
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Can ATX PSU blow the mainboard?
On Fri, 1 Nov 2013 08:42:58 +0000 (UTC), TMack
wrote: On Fri, 01 Nov 2013 08:31:24 +0000, Niel Humphreys wrote: It would be nice to know a proposed mechanism for this difference between Intel and AMD systems. Intel CPUs have built in heat/voltage protection, AMD processors do not which is why AMDs tend to be cheaper. Er... no, not really for that reason. The economics of chip production are complicated. For instance, when the cooling protection fails on an Intel CPU it just slows down and grinds to a halt until it cools down then works fine again. With AMD they just fry and usually take the motherboard with them. The same for voltage spikes etc. That might have been true about 10 years ago but not now. All AMD CPUs since the Athlon64 have on-die thermal protection. I'm pretty sure that AMD got it first, too - out of necessity, since the early AMD's ran rather hot! Cheers - Jaimie -- "It's people like that who make you realize how little you've accomplished. It is a sobering thought, for example, that when Mozart was my age, he had been dead for two years" - Tom Lehrer |
#12
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Can ATX PSU blow the mainboard?
TMack wrote:
On Fri, 01 Nov 2013 08:31:24 +0000, Niel Humphreys wrote: It would be nice to know a proposed mechanism for this difference between Intel and AMD systems. Intel CPUs have built in heat/voltage protection, AMD processors do not which is why AMDs tend to be cheaper. For instance, when the cooling protection fails on an Intel CPU it just slows down and grinds to a halt until it cools down then works fine again. With AMD they just fry and usually take the motherboard with them. The same for voltage spikes etc. That might have been true about 10 years ago but not now. All AMD CPUs since the Athlon64 have on-die thermal protection. My AthlonXP motherboard, it monitored diode temperature on the processor. The processor has a thermal diode on the silicon die (cathode and anode pinned out). The motherboard designer connected that to an 8 pin chip, and the output of the chip fed into the PS_ON# logic. The end result was, if the heatsink fell off the processor, my power supply would be shut off instantly. Since diode monitoring is right on the die, there is no lag compared to waiting for a socket thermistor to heat up. The latency is zero. The eight pin chip requires no software, so even if the BIOS crashed, the motherboard still shut off. And that design, is an example of correcting for a couple of faults with previous protection concepts. No software needed to react. It's true, a previous generation of S462 Athlon didn't have effective protection. It might even have been the case, that the thermal diode was on the processor all along, but wasn't specified in the design examples, as being necessary. (The diode may have existed, for AMD staff in the lab, to qualify cooling solutions.) I think the later generations (S754, S939, AM2 and so on), they have THERMTRIP. Which replaces the eight pin chip my board had, and does it all inside the processor. So now, a signal comes from the processor, specifically for turning off the ATX supply. The heatsink can fall off a S939, and the power supply gets shut off when the CPU is sufficiently warm. The AMD website is so pathetic now, I no longer try to find what pass for datasheets, to fill in details. I can only assume that THERMTRIP has been a standard feature to this day. Throttling is another question. AMD supports P-State changes, and software could change states on a mild overheat. You don't want to rely on THERMTRIP, because it's going to leave a dirty shutdown on filesystems and need CHKDSK. ******* A voltage spike is a completely different animal. Since there can be switching converters for Vcore and various DIMM voltages, those converters provide a measure of isolation between the ATX PSU and some of the plugin components. The motherboard itself could be an easy victim, if any motherboard logic runs off a rail directly. So I cannot discount a Bestec-like event taking out a motherboard, but your CPU and RAM might be reusable. The hard drive, because it connects directly to the ATX supply, could also be a victim. The logic board on there, has a protection device that clips overvoltage. Like, if the +12V feeding the motor rises to around +15V, there is a protection device near the power supply terminals that gets burned. That device is there to prevent inductive spiking when a hard drive is removed "hot". It is not intended to crowbar an ATX supply, and cause the ATX supply fuse to blow. So the hard drive, one of the things that happens, is the two protection devices (one on +5, one on +12) fry, and the logic board, motor controller fry next. Any sustained overvoltage, for periods of seconds, will ruin the drive. The drive is protected to some extent, against millisecond long inductive spikes. A Bestec, would just burn the protection device on +5V. A poster here, pointed out these things to me. He posted that he had a hard drive, and a couple components near the power supply connector were burned. And using numbers off a similar logic board, we figured out those components were for overvoltage protection. So this isn't something I read on a web site - it was discovered while mulling over some visual symptoms on a hard drive. (The only other thing that likes to burn on hard drives, is particular models of motor controllers :-) ) Paul |
#13
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Can ATX PSU blow the mainboard?
On 01:55 31 Oct 2013, Johny B Good wrote:
On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote: Can an overheating ATX PSU blow the mainboard if the PSU fails? I may be mistaken but ISTR there's a possibility of a voltage surge when the PSU goes. Apart from the well known infamous Bestec ATX psus used by eMachines models harking back a decade ago, most ATX PSUs fail without damaging the MoBo. The usual failure mode when SMPSUs overheat is for the switching transistors in the HT module to go short circuit and smash the safety fuse to smithereens in a flash of light accompanied by a loud pop and a trace of smoke. When a PSU shuffles off its mortal coil with such drama, only a single modest transient voltage spike appears on the voltage rails (the very small ferrite transformer can only transfer a limited amount of power due to such a _single_ terminal pulse of current) which is incapable of causing damage. IOW, the kindest failure mode wrt the load is that dramatic sudden fuse shattering failure of the switching transistors in the HT module. There are other types of failure involving sustained overvoltage but these tend to be rare unless the manufacturer goes out of his way to bypass/ignore the overload/overvoltage protection features built into all the standard smpsu controller chips that made it possible to manufacture ATX psus at all in large volumes at affordable prices. If the ATX PSU in question went "BANG!", then it's most likely that no harm has been done and a drop in replacement ATX PSU will get things working again. I'm the OP for this thread. The fan on my ATX PSU seems to slow down at times and makes a noise so I guess it's approaching the end of its life. My PSU has not overheated yet and I'm still using the PC until I manage to change the PSU or maybe just the fan. Can you help me with this? ... If my PSU does overheat and might fry the mainboard then would a surge protector on the incoming mains prevent the PSU suddenly drawing mains power to feed the surge? (I'm in the UK where I understand the mains voltage tends to be reasonably stable.) |
#14
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Can ATX PSU blow the mainboard?
On Fri, 01 Nov 2013 09:36:47 +0000, Jaimie Vandenbergh wrote:
That might have been true about 10 years ago but not now. All AMD CPUs since the Athlon64 have on-die thermal protection. I'm pretty sure that AMD got it first, too - out of necessity, since the early AMD's ran rather hot! Nope, Pentiums had it first. Tom's Hardware circa 2001 demonstrated Athlons burning up and Pentiums surviving when the hs/fan was removed. -- Tony '09 FJR1300, '87 TW200, 89 TW200, '07 Street Triple OMF#24 |
#15
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Can ATX PSU blow the mainboard?
On Wed, 30 Oct 2013 21:23:54 -0000, Jason wrote:
Can an overheating ATX PSU blow the mainboard if the PSU fails? I may be mistaken but ISTR there's a possibility of a voltage surge when the PSU goes. Definitely yes, it can happen. Bestec PSU's were renowned for destroying mainboards when they failed. I've also seen PSU failures kill virtually every other part in the system. I recall one system where only a PCI 56k modem and a floppy disc drive survived. HDD, DVD drive, CPU, memory, gfx card were all dead - even the cpu cooler fan had died. This is precisely why cheap n' cheerful PSU's should be avoided. |
#16
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Can ATX PSU blow the mainboard?
En el artículo , Jason
escribió: I'm the OP for this thread. The fan on my ATX PSU seems to slow down at times and makes a noise so I guess it's approaching the end of its life. My PSU has not overheated yet How do you know? and I'm still using the PC until I manage to change the PSU or maybe just the fan. It'll be too late by then. The PSU will have heated to the point that the caps inside are damaged and no longer adequately smooth the output voltages. When that happens, the motherboard caps, placed under abnormal stress also begin to fail. The time to change out your PSU is now, before motherboard damage occurs. would a surge protector on the incoming mains prevent the PSU suddenly drawing mains power to feed the surge? No, not at all. It deals with a surge on the *input*, not on the output. (I'm in the UK where I understand the mains voltage tends to be reasonably stable.) For now, but the Grid is approaching a point where backup capacity to deal with unexpected outages (like Dungeness nuke station tripping offline during last week's storms) is becoming marginal because so many power stations, mainly coal burners, have been forced to close to comply with Euro environmental ********. This winter, expect brownouts at best and blackouts at worst. If no more generating capacity is brought online next year and we can't import enough power from the cloggies and frenchies over the interconnects, blackouts *will* occur next winter. -- (\_/) (='.'=) (")_(") |
#17
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Can ATX PSU blow the mainboard?
En el artículo , TMack
escribió: Nope, Pentiums had it first. Tom's Hardware circa 2001 demonstrated Athlons burning up and Pentiums surviving when the hs/fan was removed. http://jasper.org.uk/THG_CPU_Cooling.avi Amazing to think that was nearly 14 years ago. -- (\_/) (='.'=) (")_(") |
#18
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Can ATX PSU blow the mainboard?
On Fri, 01 Nov 2013 16:32:27 GMT, Jason wrote:
On 01:55 31 Oct 2013, Johny B Good wrote: On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote: Can an overheating ATX PSU blow the mainboard if the PSU fails? I may be mistaken but ISTR there's a possibility of a voltage surge when the PSU goes. Apart from the well known infamous Bestec ATX psus used by eMachines models harking back a decade ago, most ATX PSUs fail without damaging the MoBo. The usual failure mode when SMPSUs overheat is for the switching transistors in the HT module to go short circuit and smash the safety fuse to smithereens in a flash of light accompanied by a loud pop and a trace of smoke. When a PSU shuffles off its mortal coil with such drama, only a single modest transient voltage spike appears on the voltage rails (the very small ferrite transformer can only transfer a limited amount of power due to such a _single_ terminal pulse of current) which is incapable of causing damage. IOW, the kindest failure mode wrt the load is that dramatic sudden fuse shattering failure of the switching transistors in the HT module. There are other types of failure involving sustained overvoltage but these tend to be rare unless the manufacturer goes out of his way to bypass/ignore the overload/overvoltage protection features built into all the standard smpsu controller chips that made it possible to manufacture ATX psus at all in large volumes at affordable prices. If the ATX PSU in question went "BANG!", then it's most likely that no harm has been done and a drop in replacement ATX PSU will get things working again. I'm the OP for this thread. The fan on my ATX PSU seems to slow down at times and makes a noise so I guess it's approaching the end of its life. My PSU has not overheated yet and I'm still using the PC until I manage to change the PSU or maybe just the fan. The fan is simply showing a lack of lubrication, try cleaning all the dust and fluff (vacuum and a 1/2 inch paintbrush makes an effect combination) before putting a drop or two of oil into the fan spindle bearing (rubber plug hidden beneath the manufaturer's sticker). This should, at the very least, extend the life of the PSU (assuming the fan responds favourably - as they typically do - to such treatment). You can check the PCB for any obviously 'blown' caps whilst you've got the cover off although, ime, replacing any such caps is far from guaranteed to extend the life of the PSU (a far cry from the effect of replacing such caps on a MoBo where it usually extends the service life by a year or three) Can you help me with this? ... If my PSU does overheat and might fry the mainboard then would a surge protector on the incoming mains prevent the PSU suddenly drawing mains power to feed the surge? If the fan stops completely, the most likely failure will be the HT switching transistors going short (a flash and a bang) which is generally not likely to trouble any of its rails with a voltage spike worthy of such a description (more likely a voltage blip). As for the use of a surge protector this won't make any difference as far as your theory of failure mode is concerned. However, it can reduce the risk of a voltage spike triggering an 'avalanche' failure due to excess temperature reducing the collector/drain breakdown voltage of the HT switching devices. Do you have a particularly bad mains supply with regard to spike voltages? (I'm in the UK where I understand the mains voltage tends to be reasonably stable.) You've got that right! Here in the UK you just don't get the same UPS ROI benefit as they do in most parts of the US of A. :-) -- Regards, J B Good |
#19
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Can ATX PSU blow the mainboard?
On Thu, 31 Oct 2013 20:47:12 -0400, Paul wrote:
Niel Humphreys wrote: "Jason" wrote in message ... Can an overheating ATX PSU blow the mainboard if the PSU fails? I may be mistaken but ISTR there's a possibility of a voltage surge when the PSU goes. If it's an Intel based system then it is unlikely but if it is an AMD based system it could well take the board and processor out with it. I have to ask, what makes one more "prone" than the other ? I haven't any first-hand experience with the problematic Bestec, but I understand that one, damages a computer because the +5V output goes to around +8V and damages all the hardware in the system that uses +5V. Wrong supply rail. It was the 5VSB rail that was susceptible to overvolting. Typically the voltage would (presumably) creep up little by little, reaching voltages in excess of 6v, typically 7[1] to 9 volts being observed ime. Quite obviously, due to such overvolting failures only being observed with these particular Bestec supplies, there was no effective overvolting protection circuit on the 5VSB rail. An unfortunate oversight since this powers all the standby circuitry of the MoBo (RTC and PS Button monitoring circuitry) which remains exposed to the steadily rising voltage even when the PC is shutdown whilst it continues to recieve mains power (few users will go to the trouble of switching off at the mains post shutdown). In the case of a "voltage surge", as proposed, the processor has a switching converter (VCore) located around the CPU socket. The switching converter provides conversion and a degree of isolation, between +12V coming into it, and the approximately +1V feeding the core of the processor. And that is proposed as a protection mechanism for the processor - the existence of another power conversion stage. A few of the motherboard subsystems are like that, having onboard regulation which can provide some protection. The motherboard could still blow out, if a voltage shoots high enough, but it doesn't really matter what brand of CPU when that happens. You will likely get to reuse your CPU and RAM, as they're not directly exposed. That's a valid mechanism of protection for those particular items. It would be nice to know a proposed mechanism for this difference between Intel and AMD systems. The AMD cpus up to and including the Socket A XP series had no built in thermal throttling which I believe was introduced by Intel with its P2/P3 processors (possibly only the socket 370 chips). I don't think I ever came across any dead or shorted Intel CPUs ever but I certainly saw a few dead or shorted AMD ones (outside of the box of 6 or 7 2nd user socket A chips bought from a flea market trader for a fiver out of which only two actually worked - most of the rest, as expected, proving to be short circuit[2]) [1] 7 volts is the maximum Vcc (10 seconds) electrical stress limit for TTL (and the CMOS drop in equivilents). [2] Anticipating such MoBo destroying faults, I powered up with my eyes on the Metrawatt Watt meter, switched to the 200v 1A range, and my other hand poised to operate the PSU mains isolator switch in the event that the wattage exceeded 120 (no disk drives, just the bare minimum hardware required to allow a successful POST sequence to be observed). Testing the shorted CPUs produced a wattage reading that immediately went north of the 200 watt mark on the scale (in fact pegging the needle hard against the end stop) for the half second it took to register the reading _and_ hit the off switch. Unfortunately, this test carries too high a risk when using a digital watt meter, you really do need an analogue meter for this sort of test. -- Regards, J B Good |
#20
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Can ATX PSU blow the mainboard?
Johny B Good wrote:
On Thu, 31 Oct 2013 20:47:12 -0400, Paul wrote: Niel Humphreys wrote: "Jason" wrote in message ... Can an overheating ATX PSU blow the mainboard if the PSU fails? I may be mistaken but ISTR there's a possibility of a voltage surge when the PSU goes. If it's an Intel based system then it is unlikely but if it is an AMD based system it could well take the board and processor out with it. I have to ask, what makes one more "prone" than the other ? I haven't any first-hand experience with the problematic Bestec, but I understand that one, damages a computer because the +5V output goes to around +8V and damages all the hardware in the system that uses +5V. Wrong supply rail. It was the 5VSB rail that was susceptible to overvolting. Typically the voltage would (presumably) creep up little by little, reaching voltages in excess of 6v, typically 7[1] to 9 volts being observed ime. Quite obviously, due to such overvolting failures only being observed with these particular Bestec supplies, there was no effective overvolting protection circuit on the 5VSB rail. An unfortunate oversight since this powers all the standby circuitry of the MoBo (RTC and PS Button monitoring circuitry) which remains exposed to the steadily rising voltage even when the PC is shutdown whilst it continues to recieve mains power (few users will go to the trouble of switching off at the mains post shutdown). In the case of a "voltage surge", as proposed, the processor has a switching converter (VCore) located around the CPU socket. The switching converter provides conversion and a degree of isolation, between +12V coming into it, and the approximately +1V feeding the core of the processor. And that is proposed as a protection mechanism for the processor - the existence of another power conversion stage. A few of the motherboard subsystems are like that, having onboard regulation which can provide some protection. The motherboard could still blow out, if a voltage shoots high enough, but it doesn't really matter what brand of CPU when that happens. You will likely get to reuse your CPU and RAM, as they're not directly exposed. That's a valid mechanism of protection for those particular items. It would be nice to know a proposed mechanism for this difference between Intel and AMD systems. The AMD cpus up to and including the Socket A XP series had no built in thermal throttling which I believe was introduced by Intel with its P2/P3 processors (possibly only the socket 370 chips). I don't think I ever came across any dead or shorted Intel CPUs ever but I certainly saw a few dead or shorted AMD ones (outside of the box of 6 or 7 2nd user socket A chips bought from a flea market trader for a fiver out of which only two actually worked - most of the rest, as expected, proving to be short circuit[2]) [1] 7 volts is the maximum Vcc (10 seconds) electrical stress limit for TTL (and the CMOS drop in equivilents). [2] Anticipating such MoBo destroying faults, I powered up with my eyes on the Metrawatt Watt meter, switched to the 200v 1A range, and my other hand poised to operate the PSU mains isolator switch in the event that the wattage exceeded 120 (no disk drives, just the bare minimum hardware required to allow a successful POST sequence to be observed). Testing the shorted CPUs produced a wattage reading that immediately went north of the 200 watt mark on the scale (in fact pegging the needle hard against the end stop) for the half second it took to register the reading _and_ hit the off switch. Unfortunately, this test carries too high a risk when using a digital watt meter, you really do need an analogue meter for this sort of test. I just found an analysis on this site. Amazing. I didn't know any details from the Bestec era, just that you should swap out a ATX-250-12E if you happened to own one. They do a bit of a workup, here. http://www.badcaps.net/forum/showthread.php?p=69599 The original and modified (hand drawn) schematics for the +5VSB section, are copied here. The poster in that thread, repairs the Bestec with a new design for the +5VSB section. "Bestec ATX 250 12E original.gif" http://imageshack.us/a/img208/3773/9b7a.gif "Bestec ATX 250 12E modified.gif" http://imageshack.us/a/img96/2793/n8qj.gif ******* "Death of a Gutless Wonder II: The Best of the Bestec" http://www.jonnyguru.com/modules.php...tory4&reid=154 "The 5VSB circuit proved to house a simple double transistor switcher working in conjunction with... surprise... a bad capacitor and no overvoltage protection circuitry." The TPS3510 only monitors three rails, so can't be relied on if there is a problem with the others. The diode connection to Vsb, isn't for monitoring, and is to keep the chip powered while the power supply is in soft-off. http://www.ti.com/lit/ds/symlink/tps3510.pdf ******* For comparison, if we look at this schematic http://www.pavouk.org/hw/en_atxps.html the lower left corner shows a +5VSB implementation. What I like about it, is it is followed by a 78L05, a linear regulator. That might have protected the +5VSB rail a bit better, but such a design would be underpowered for modern systems (which run +5VSB at up to 3 amps). A linear is highly inefficient, but that last chip offers some protection against a few faults. It's not going to be as good as a full featured +5VSB designed by someone who cares. ******* What the above doesn't square with, was at the time, I was reading about hard drives being ruined by the Bestec. If it was +5VSB that was failing, that doesn't power the hard drive. The damage path would be a lot longer, to get from +5VSB into the 5V rail powered stuff. Back when I was reading up on this stuff, there were reports of "5V going to 8V" and "motherboard and hard drive ruined". To explain what I mean by a damage path, I can give an example from a lab accident. I was using a logic analyser, on a system with an open faced power supply. One of the test leads, fell into the supply (120V). I heard a pop. I thought the analyser was destroyed for sure. When the instrument was sent to our inhouse service shop, the guy in there (a rocket scientist), fixed it in two days, and only two ECL chips were ruined. So unlike the Byte Magazine example where "all the tops of the chips were blown off", contact with AC didn't actually work its way too far into the instrument. Some chips die, in order that others can live :-) Figuratively speaking... The more items a fault has to go through, the more the effects get attenuated. Paul |
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