Author Topic: Why aren't computers designed to handle power failure?  (Read 12739 times)

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Online SiliconWizard

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Re: Why aren't computers designed to handle power failure?
« Reply #25 on: June 12, 2020, 01:40:15 pm »
As said. Cost, usefulness. Complexity. (That would be another potential point of failure and something to maintain - the batteries for instance.)

As someone else said, thanks to reasonable filesystems and reasonable OSs, most computers can survive power loss with no harm done. I've certainly experienced quite a few in the past (before I used UPSs) and never damaged anything or lost any file due to that.

Now if you want that very feature, it's easy. Buy a laptop.
 

Offline pepelevamp

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Re: Why aren't computers designed to handle power failure?
« Reply #26 on: June 12, 2020, 02:20:26 pm »

Also comp sci guy. None of that really matters. All you need is a write barrier and transactional consistency. And we actually mostly have that.

In a lot of cases we have much much much better than that with journaling and nice new formats (Redis AOF I fucking love) which allow full ordered consistency.
yeah thats beautiful stuff. but saying ya only need transactional consistency is like saying 'its easy. to solve this problem all ya need is the problem solved'. how ya gonna get transactional consistency into a multi-core SMP dude-bro PC with shared and non-shared caches and no atomic operations? :(

non-volatile memory is the ticket to all dis. CPUs can shut down & live on 0.001mA no problem but not dram.

I had this old 286 with non-volatile memory. This old rugged handheld unit that weighed like over 2kg in your hand & was made of IRON & nickel or something. you could break a car window with it. ya could take out the batteries for up to 30 days and put em back in and resume ya work. No jokes. Little LCD screen with AA batteries. thats the kind of tough computer that bullies you into doing the work for it.
 

Offline krish2487

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Re: Why aren't computers designed to handle power failure?
« Reply #27 on: June 12, 2020, 02:38:19 pm »
Going on a tangent here.. One reason I can think of why most UPS systems are not DC and AC is also the overall cost of transmission.
It is pretty much the same reason why transmit AC rather than DC. Not withstanding small UPS systems which you place next to your PC, even a moderately sized installation for a couple of computers or even a small office will
1. Not run off a single 12V, but a higher DC bus
2. Cost of wiring to handle will be way expensive compared to a AC installation of a similar size. All the switchgear, safety circuits, wires will need to sized for DC.

If god made us in his image,
and we are this stupid
then....
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #28 on: June 12, 2020, 02:41:07 pm »

Also comp sci guy. None of that really matters. All you need is a write barrier and transactional consistency. And we actually mostly have that.

In a lot of cases we have much much much better than that with journaling and nice new formats (Redis AOF I fucking love) which allow full ordered consistency.
yeah thats beautiful stuff. but saying ya only need transactional consistency is like saying 'its easy. to solve this problem all ya need is the problem solved'. how ya gonna get transactional consistency into a multi-core SMP dude-bro PC with shared and non-shared caches and no atomic operations? :(

non-volatile memory is the ticket to all dis. CPUs can shut down & live on 0.001mA no problem but not dram.

I had this old 286 with non-volatile memory. This old rugged handheld unit that weighed like over 2kg in your hand & was made of IRON & nickel or something. you could break a car window with it. ya could take out the batteries for up to 30 days and put em back in and resume ya work. No jokes. Little LCD screen with AA batteries. thats the kind of tough computer that bullies you into doing the work for it.

I disagree. You're looking at one side of the set of problems.

Memory consistency is irrelevant to the point. Your data is divided neatly into volatile and non volatile across a neat line in the storage hierarchy. You only need consistency across the volatility barrier, which you get from write barriers and transaction journaling. But that's not even the issue.

As for transactional consistency I write highly concurrent, redundant and reliable code that works across NUMA machines with 48 cores and 1Tb+ of RAM. I suggest you read Hoare's CSP paper as an introduction to my favoured approach which doesn't need transactional memory or global atomicity. The reason none of that got implemented in our current state of the art architectures is because quite frankly it sucked.

Complete non-volatility is distinctly NOT an option because you're only looking at power failure for one set of state. The entire machine's state consists of thousands of little pockets of state from IO registers, DRAM buffers, SMC registers, SPI bus transactions, PCI bus transactions in flight, CPU configuration registers etc. And we're only looking at the power failure scenario. How do we handle hardware failures or bus errors (sweep them under the carpet?). None of that can't be consistently rationalised by hardware really. As always it's easier to resolve the case of how to get from ground zero to a known state than it is to get from an unknown state to a known state.

However the short cut and the correct answer is that the only thing that matters is the intent of what you are doing and recovering that intent from your non volatile store. So all you have to do is:

1. make sure the intent is consistent on the part of the software writing to disk (sync + transaction journalling)
2. that the data is written in an order that makes sense (write barriers)
3. that the operation succeeds (last sata / nvme transaction was committed - hold up capacitors)

This works for more than just power failure scenarios. Fires, halon dumps, APC UPS issues, wars, dodgy fibre cables and laptop PMC's giving up before the battery is dead.
 

Offline pepelevamp

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Re: Why aren't computers designed to handle power failure?
« Reply #29 on: June 12, 2020, 02:53:12 pm »

Also comp sci guy. None of that really matters. All you need is a write barrier and transactional consistency. And we actually mostly have that.

In a lot of cases we have much much much better than that with journaling and nice new formats (Redis AOF I fucking love) which allow full ordered consistency.
yeah thats beautiful stuff. but saying ya only need transactional consistency is like saying 'its easy. to solve this problem all ya need is the problem solved'. how ya gonna get transactional consistency into a multi-core SMP dude-bro PC with shared and non-shared caches and no atomic operations? :(

non-volatile memory is the ticket to all dis. CPUs can shut down & live on 0.001mA no problem but not dram.

I had this old 286 with non-volatile memory. This old rugged handheld unit that weighed like over 2kg in your hand & was made of IRON & nickel or something. you could break a car window with it. ya could take out the batteries for up to 30 days and put em back in and resume ya work. No jokes. Little LCD screen with AA batteries. thats the kind of tough computer that bullies you into doing the work for it.

I disagree. You're looking at one side of the set of problems.

Memory consistency is irrelevant to the point. Your data is divided neatly into volatile and non volatile across a neat line in the storage hierarchy. You only need consistency across the volatility barrier, which you get from write barriers and transaction journaling. But that's not even the issue.

As for transactional consistency I write highly concurrent, redundant and reliable code that works across NUMA machines with 48 cores and 1Tb+ of RAM. I suggest you read Hoare's CSP paper as an introduction to my favoured approach which doesn't need transactional memory or global atomicity. The reason none of that got implemented in our current state of the art architectures is because quite frankly it sucked.

Complete non-volatility is distinctly NOT an option because you're only looking at power failure for one set of state. The entire machine's state consists of thousands of little pockets of state from IO registers, DRAM buffers, SMC registers, SPI bus transactions, PCI bus transactions in flight, CPU configuration registers etc. And we're only looking at the power failure scenario. How do we handle hardware failures or bus errors (sweep them under the carpet?). None of that can't be consistently rationalised by hardware really. As always it's easier to resolve the case of how to get from ground zero to a known state than it is to get from an unknown state to a known state.

However the short cut and the correct answer is that the only thing that matters is the intent of what you are doing and recovering that intent from your non volatile store. So all you have to do is:

1. make sure the intent is consistent on the part of the software writing to disk (sync + transaction journalling)
2. that the data is written in an order that makes sense (write barriers)
3. that the operation succeeds (last sata / nvme transaction was committed - hold up capacitors)

This works for more than just power failure scenarios. Fires, halon dumps, APC UPS issues, wars, dodgy fibre cables and laptop PMC's giving up before the battery is dead.

Valid. I yield to your logic.

I'm still taking with me though my rant about computers being full of fibs & lies. I'm still afraid of intel's spooky-ghost execution and ya cant make me like it!
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #30 on: June 12, 2020, 02:54:45 pm »
Oh yes that's a complete shit show that is. Completely agree. And don't get me started on x86 as an architecture  :-DD

Edit: incidentally http://danluu.com/cpu-bugs/. Ryzen here. Slightly less buggy  :-DD
« Last Edit: June 12, 2020, 02:56:21 pm by bd139 »
 

Offline filssavi

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Re: Why aren't computers designed to handle power failure?
« Reply #31 on: June 12, 2020, 02:57:55 pm »
Just make it an ATX PSU with a standardized connection for a battery and USB for monitoring. In fact, with many modern ATX PSUs internally generating 5V and 3.3V from 12V using DC/DC converters and a 3S pack being just perfect for supplying 12V directly, it might not take much hacking to convert a PSU to do that.

What I would like to see is an additional signal that instantly drops the CPU speed to minimum to allow using a smaller battery, I have DIYed one fairly easily by adding a circuit to a motherboard that pulls down the PROCHOT line.

If you want a one off prototype/ small production run I am shute you can hack together something that sort of works with a battery, am arduino and not much more

That said the question was why is not a standard feature of all PCs. In that case with the volumes we are talking about, coupled to how anal the enthusiast market is (just waiting for the smallest technicality to raise a major shitstorm against anyone) you need something much better engineered and integrated.

The hard part is the software not the hardware, and not from a CS perspective, it is the software engineering that kills you, making sure everything is compatible, right drivers, client software must not be too obstructive, backward compatibility, etc
 

Offline ogden

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Re: Why aren't computers designed to handle power failure?
« Reply #32 on: June 12, 2020, 02:59:54 pm »
This would be most efficient if the battery were to directly interact with the motherboard.
Why don't we do this?
We indeed do this. In every laptop and tablet/handheld computer. Some time ago Google did that with server as well - gel battery plugged directly into motherboard. https://www.cnet.com/news/google-uncloaks-once-secret-server-10209580/
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #33 on: June 12, 2020, 03:02:59 pm »
Just make it an ATX PSU with a standardized connection for a battery and USB for monitoring. In fact, with many modern ATX PSUs internally generating 5V and 3.3V from 12V using DC/DC converters and a 3S pack being just perfect for supplying 12V directly, it might not take much hacking to convert a PSU to do that.

What I would like to see is an additional signal that instantly drops the CPU speed to minimum to allow using a smaller battery, I have DIYed one fairly easily by adding a circuit to a motherboard that pulls down the PROCHOT line.

If you want a one off prototype/ small production run I am shute you can hack together something that sort of works with a battery, am arduino and not much more

That said the question was why is not a standard feature of all PCs. In that case with the volumes we are talking about, coupled to how anal the enthusiast market is (just waiting for the smallest technicality to raise a major shitstorm against anyone) you need something much better engineered and integrated.

The hard part is the software not the hardware, and not from a CS perspective, it is the software engineering that kills you, making sure everything is compatible, right drivers, client software must not be too obstructive, backward compatibility, etc

BTW you can use "picopsu" boards to do this and then use a standard BMC board as the supply for it.

https://www.mini-itx.com/store/?c=10

Don't expect to hang a Ryzen 9 off it  :-DD
 

Offline pepelevamp

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Re: Why aren't computers designed to handle power failure?
« Reply #34 on: June 12, 2020, 03:22:38 pm »
BTW you can use "picopsu" boards to do this and then use a standard BMC board as the supply for it.
https://www.mini-itx.com/store/?c=10

Don't expect to hang a Ryzen 9 off it  :-DD
thanks a bunch now i have lost the rest of my life to this rabbit hole. what a fantastic idea. I have long wished that all the devices in my house simply ran off DC. you could have a stack of 18650s in there with a BMS and have your own sweet sensual UPS for a fraction of the cost of those horrible big nasty UPSes that just include those disgusting alternators with their jaggedy excuses for sine waves.
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #35 on: June 12, 2020, 03:27:24 pm »
I was working on a similar idea until recently. Decided not to bother in the end because the incompatibilities of all the things gave me a small headache every time I tried to resolve them  :(. I have an SLA floating around, some LED lights that'll run of it, a laptop with extended battery and a Trangia stove worst case
 

Offline Marco

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Re: Why aren't computers designed to handle power failure?
« Reply #36 on: June 12, 2020, 03:33:26 pm »
This would be most efficient if the battery were to directly interact with the motherboard.
Why don't we do this?
Cause no one big pushed it. If the ATX standard even had as an option a standardized DC input for UPS purposes, then things would have gone differently.
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #37 on: June 12, 2020, 03:42:08 pm »
There's an ATX12VO standard coming out this year which is standardised DC input for 12V. Design guide: https://www.intel.com/content/dam/www/public/us/en/documents/guides/single-rail-power-supply-platform-atx12vo-design-guide.pdf
 
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Offline filssavi

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Re: Why aren't computers designed to handle power failure?
« Reply #38 on: June 12, 2020, 03:48:06 pm »
There's an ATX12VO standard coming out this year which is standardised DC input for 12V. Design guide: https://www.intel.com/content/dam/www/public/us/en/documents/guides/single-rail-power-supply-platform-atx12vo-design-guide.pdf

True but At least in the foreseeable future it will only be used in OEM systems ( think dell, HP and Lenovo) Discrete PSU and motherboard manufacturers have already said they don’t have any plan to implement it as it would fragment the market and lead to confusion in most consumers
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #39 on: June 12, 2020, 04:16:36 pm »
That's a bummer. There's enough fragmentation so I agree. I built my first desktop for about 10 years recently and was annoyed to find out that I still had to frig around with LED and power switch wiring like I did in the mid 1990s. Perhaps they can consolidate all that first.
 

Offline filssavi

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Re: Why aren't computers designed to handle power failure?
« Reply #40 on: June 12, 2020, 04:52:22 pm »
I wholeheartedly agree with you, I personally think that in the long run always staying up to date as much as possible saves a load of time and headache.
Unfortunately the rest of the computing world seems to revolve around lazy peoples, and either you go the apple route, discontinuing and changing what you want, and are thorougly hated for that, or you keep backwards compatibility essentially forever (ok usually 15/30 years, which is pretty much forever), as anyone else does.
This means that no standard can be retired, and the infamous 14 standards xkcd is pretty much the only thing that happens

Case and point the IPv4 to IPv6 transition, it has been going on for 20 years and will not be finished at least until 2040 in my opinion, all the while ipv4 is on life support (many peoples ask ARINC to issue also the 240.0.0.0/4 space, knowing full well that at the moment most of the routers on the planet do not support them, since they were not supposed to be used).
 

Offline RajTopic starter

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Re: Why aren't computers designed to handle power failure?
« Reply #41 on: June 12, 2020, 05:12:06 pm »
"people won't like to replace batteries"
Meanwhile, we third world guys have to deal with using desktops cause it's too hot for laptops to not thermal throttle. But the ups are so horrible, they just save your pc from dying twice, then the battery is useless (doesn't keep the PC alive it'll it's done shutting down)

I’m sorry if I came out rude, it really was not my intention. I feel your pain, however the fact of the matter is that development in PC technology is driven by developed “first world” countries needs, and here the power grids are stable enough that the odd crash once or twice a year is not an issue.

Bolting the feature on after the fact is certainly doable, whether you can find a market large enough for it to be economically viable I’m not knowledgeable enough on markets where such a thing would be usefull

No, no, you weren't rude at all... Just, you didn't know what people of other countries going through

Quote from: Ian.M
link=topic=244295.msg3094425#msg3094425 date=1591960180]
ATX form factor combo PSU/UPSes are commercially available. Its a niche market but big enough to support a number of manufacturers.
e.g. http://embedded-computing.com/news/trumpower-24v-battery-charger-2/
No special motherboard support required except for a free internally accessible USB port.
I didnt know that... Thanks

Samsung Pro 2.5" SATA units are fine as well. I found that the Samsung Pro M2 ones don't have hold up capacitors though as they are usually shoved in laptops. Figured to hell with it when I built my desktop and stuffed a Samsung Evo in it.  :-//

HPE and Intel ones do.
Lucky me, has a Samsung
** computer science guy joins the chat

the modern day CPU is full of lies & tricks to get more performance by cheating. writing to local caches etc. its all a big scam. pipe-lining, speculative execution, asynchronous volatile buffers - its all stuff that takes away your ability to deterministically run operations in sequence - all just so you can get more overall throughput.
Yup, spectre and meltdown were pretty bad. But 97% performace degradation after patch? Wow! I didnt know that

Quote from: engrguy42

Also, W10 has a (sometimes annoying) feature where if it's shut off suddenly it remembers what you were working on and re-starts it all, where you left off, the next time you boot your computer.

That's why I like to use alt f4 instead of start menu. Man that stuff is super annoying

What is the point of connecting a battery directly to the desktop computer if it is often required to also keep the display powered and may be some other peripherals. A mains voltage UPS already does that.
Since doing that will provide longer standby time with same battery otherwise one could always get "inverter" which can literally power a computer almost 40 times as long (I know that inverter battery is marked 150Ah and ups battery is marked 7Ah, but it's it really? Measure it and 7Ah will come out as 2Ah, since all of them are made by no name brand with no one caring to test em)

BTW you can use "picopsu" boards to do this and then use a standard BMC board as the supply for it.
https://www.mini-itx.com/store/?c=10

Don't expect to hang a Ryzen 9 off it  :-DD
thanks a bunch now i have lost the rest of my life to this rabbit hole. what a fantastic idea. I have long wished that all the devices in my house simply ran off DC. you could have a stack of 18650s in there with a BMS and have your own sweet sensual UPS for a fraction of the cost of those horrible big nasty UPSes that just include those disgusting alternators with their jaggedy excuses for sine waves.
I too am trying to literally modify everything I own, to run off of 18650

That's a bummer. There's enough fragmentation so I agree. I built my first desktop for about 10 years recently and was annoyed to find out that I still had to frig around with LED and power switch wiring like I did in the mid 1990s. Perhaps they can consolidate all that first.
Here's a tip, arrange them then hot glue em and then connect and peel the glue off. That way, you'll have to fumble around less

I wholeheartedly agree with you, I personally think that in the long run always staying up to date as much as possible saves a load of time and headache.
Unfortunately the rest of the computing world seems to revolve around lazy peoples, and either you go the apple route, discontinuing and changing what you want, and are thorougly hated for that, or you keep backwards compatibility essentially forever (ok usually 15/30 years, which is pretty much forever), as anyone else does.
This means that no standard can be retired, and the infamous 14 standards xkcd is pretty much the only thing that happens

Case and point the IPv4 to IPv6 transition, it has been going on for 20 years and will not be finished at least until 2040 in my opinion, all the while ipv4 is on life support (many peoples ask ARINC to issue also the 240.0.0.0/4 space, knowing full well that at the moment most of the routers on the planet do not support them, since they were not supposed to be used).
And my isp is like adding NATs to NATs and splitting the bandwith like crazy
« Last Edit: June 12, 2020, 05:26:25 pm by Raj »
 

Offline pepelevamp

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Re: Why aren't computers designed to handle power failure?
« Reply #42 on: June 12, 2020, 05:50:52 pm »
thanks a bunch now i have lost the rest of my life to this rabbit hole. what a fantastic idea. I have long wished that all the devices in my house simply ran off DC. you could have a stack of 18650s in there with a BMS and have your own sweet sensual UPS for a fraction of the cost of those horrible big nasty UPSes that just include those disgusting alternators with their jaggedy excuses for sine waves.
I too am trying to literally modify everything I own, to run off of 18650
Oh mate. Me too. It is the best idea in the universe. I'm hooked on it. With a wee USB charger board or a boost here & there to get ya up to 5v if needed or regulate down to 3v3 - its just wonderful. the whole world should do this.
 

Online tom66

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Re: Why aren't computers designed to handle power failure?
« Reply #43 on: June 12, 2020, 06:25:17 pm »
I've had one power cut in the last 3 years.  It should be uncommon enough that it doesn't cause major issue.
 

Offline RajTopic starter

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Re: Why aren't computers designed to handle power failure?
« Reply #44 on: June 13, 2020, 05:49:42 am »
I've had one power cut in the last 3 years.  It should be uncommon enough that it doesn't cause major issue.
Meanwhile...My company is giving free power to farmers, so that they can run their bore wells, while I get a 15 minute power cut daily. The problem wouldn't be there, if the cut was to happen on a set time, but it happens randomly at any moment.
 

Offline firehopper

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Re: Why aren't computers designed to handle power failure?
« Reply #45 on: June 13, 2020, 11:48:47 am »
That's a bummer. There's enough fragmentation so I agree. I built my first desktop for about 10 years recently and was annoyed to find out that I still had to frig around with LED and power switch wiring like I did in the mid 1990s. Perhaps they can consolidate all that first.

yes I just upgraded a computer with a x570 MB and had to faf about with the front panel connectors, granted it was a lot simpler this time, as the connectors had the polarity marked on them and it was only 5 of them, so fairly easy and painless :) it just worked. but thats part of the case design.
 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #46 on: June 13, 2020, 12:04:55 pm »
Yeah mine worked first time as well which surprised me.

I did see a picture the other day where the cable had two reset button connectors on it and no LED though  :-DD
 

Offline madires

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Re: Why aren't computers designed to handle power failure?
« Reply #47 on: June 13, 2020, 01:45:09 pm »
Anything wrong with that? It's the fun part of building your own PC. ^-^
 

Online SiliconWizard

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Re: Why aren't computers designed to handle power failure?
« Reply #48 on: June 13, 2020, 04:56:16 pm »
BTW you can use "picopsu" boards to do this and then use a standard BMC board as the supply for it.
https://www.mini-itx.com/store/?c=10

Don't expect to hang a Ryzen 9 off it  :-DD
thanks a bunch now i have lost the rest of my life to this rabbit hole. what a fantastic idea. I have long wished that all the devices in my house simply ran off DC. you could have a stack of 18650s in there with a BMS and have your own sweet sensual UPS for a fraction of the cost of those horrible big nasty UPSes that just include those disgusting alternators with their jaggedy excuses for sine waves.

A number of mini-ITX motherboards can already run off DC without any additional module. Of course don't expect high performance from this, but I've built a Linux box that is on my LAN and that I use for Linux dev tasks, based on a thin mini ITX MB (ASUS) with a Core i7 4790T and 16GB RAM. Not ridiculous. Runs off a DC adapter and is fully passively cooled (the case is made for this - it gets a bit hot under load, but never failed.)


 

Offline bd139

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Re: Why aren't computers designed to handle power failure?
« Reply #49 on: June 13, 2020, 05:02:39 pm »
There are a few "canned" desktops which can do that as well. Lenovo M600's run off a 19V DC thinkpad charger

I'm using one as a media centre at the moment. Fanless Celeron that runs LibreElec + Kodi. Nice little machines. Also make handy Linux utility boxes as they run headless.
 


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