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Why Aren't PC Power Supplies External?

Cliff posted more than 12 years ago | from the modular-is-better dept.

Hardware 67

An Anonymous Coward asks: "After years in the computer industry it just occurred to me: Why don't computers have external power supplies? The lions share of the heat and noise from a computer are generated from the power supply. Why not take it out of the case and run just the 12 and 5 volt lines into the case, leaving the heat and noise tucked down under the desk somewhere? Perhaps there is some electrical law that makes that a bad idea, but I can't think of it." One stumbling block is that a power supply brings in more than the 12V and 5V lines, it also provides the power connectors for the motherboard, internal peripherals and external fans. However, these could be provided by the case. If a standard form connector from external PS to the PC is designed, might we be able to avoid further incompatibilities like AT/ATX? It's an interesting idea for future designs, but I wonder if there are other stubling blocks out there. Thoughts?

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DC outlets (3)

gjohnson (1557) | more than 12 years ago | (#264023)

I would like to see DC wall sockets. For efficiency reasons, power should be transported over long distances via AC. Once in the house, there would be one large AC -> DC converter. Jacks in the wall would have pins to select one of a few available voltages.

Look around your house/work at how many separate AC -> DC converters there are. I think centralizing would be more efficient. You could have battery backup and very clean power.

DC power is easier to use (most of the time). Telco racks are DC for a reason.

Re:Cost? (1)

stephend (1735) | more than 12 years ago | (#264024)

You need to think in terms of ecconomies of scale to get a real idea of cost in the PC industry.

When the PSU on my PC went a few months ago I found I could get a new PSU for 40 quid or a new case, with a better PSU, for 30 quid. Nobody buys PC PSU's without case or uses X-Terminals, hence the high price.

If Intel decided that an external PSU was required for ATX2, prices would plumet.

Been done! (4)

stephend (1735) | more than 12 years ago | (#264025)

In 1981 the Sinclair ZX81 had an external power supply. You reset the machine by pulling the plug from the back and reinserting it, or you could just wobble the 16K RAM pack for the same effect.

I can't wait for my new PC to have the same feature.

Re:IMHO (2)

osu-neko (2604) | more than 12 years ago | (#264026)

That's not a problem with external power supplies in general, just stupid ones. Good ones have a standard plugin, and you can plug six of them into most power strips easily. The plug in cord leads to a box, which is your power supply, another cord leads from that box to your equipment. So it's just like having a normal power cord except it's got a box in the middle, like a snake that's eaten too much...


most heat & noise from a P/S? Nope. (5)

Tumbleweed (3706) | more than 12 years ago | (#264027)

Not hardly.

These days, Most heat is generated from the CPU, and most noise, believe it or not, is generated from those cruddy little CPU fans. A lot of noise is also generated from extra case fans you may have trying to improve airflow in your case. P/S fans are often much quieter than those other fans in your system.

I've thought of this idea before, and I also think it'd be a fantastic idea. Just keep in mind, the P/S also needs to be cooled, so that external box will have fans in it, and once it's outside the case, it'll be making some noise, too. I remember my Amiga 500 fondly, though, as it's power needs were such the external P/S didn't need any fans...

Re:Clustering/Rackmounting (1)

Chris Hiner (4273) | more than 12 years ago | (#264028)

You could use the -48V DC computer power supplies that are common in telephone applications.
(Since most of the telephone switch equipment runs on -48V DC...)
They're a bit more expensive than the normal ones...
Then just use a big 110VAC to -48VDC converter, tie in a bank of batteries, and you've got the UPS end of it handled as well.

Re:Clustering/Rackmounting (1)

Chris Hiner (4273) | more than 12 years ago | (#264029)

If I remember right, it has to do with protecting
the phone lines. It helps prevent corrosion. (Alot like anodic protection for ships and such)

Cost? (5)

Bazman (4849) | more than 12 years ago | (#264030)

We had some X-terminals with external power supplies. They had a habit of breaking, so we tried to source some new ones. 80 quid (thats over $100 in USA money). I was stunned. 80 quid for a black box transformer.

Anyway, the thing had the pinout of the connector printed on the bottom, so I hacked off the cables, soldered on some standard molex connectors, and wired three of them up to a standard PC power supply running in an empty case.

Back to the question. An Xterminal is a pretty low-power-usage device (no moving parts, and the monitor was on a mains cable) and that seemed to need an expensive PSU. A comparable unit to power a PC as well would be ridiculous...


Re:Clustering/Rackmounting (2)

unitron (5733) | more than 12 years ago | (#264031)

Are you saying that telco stuff is powered by negative 48 Volts, i.e., positive ground? If so, do you happen to know why they went with that instead of negative ground?

Part of why I ask is that the local telco seems to do the which polarity is the red wire and which is the green wire backwards from most of the rest of the USA, and I'm looking for clues.

Re:IMHO (1)

turpie (8040) | more than 12 years ago | (#264032)

You put the "fucking boxes" on the fucking floor.
The crappy old laptop I've got uses a power supply like this, as does its external CD drive (creative labs). The only thing on my computer power board with a stupid power adapter is the modem, so it has to sit on a wonky angle in the board.

New Moderator options (2)

Outland Traveller (12138) | more than 12 years ago | (#264033)

In many cases, the best comments on slashdot come from people with first hand experience. It's been dissapointing that the place has been so overrun not only by trolls, but by armchair opinionists. Of course this is probably what makes the site so popular...

Still, I wish there was a moderation option called "The Horse's Mouth" or "The Straight Dope" so that people could filter on primary source comments.

That's one of the e-PC concepts (2)

TecraMan (12354) | more than 12 years ago | (#264034)

One of the changes happening in the corporate computing space is the e-PC concept (HP's e-PC, Compaq's iPaq, etc...), where alongside the smaller, quieter boxes, they're removing the PSU (HP's is actually the PSU from their notebook range). What this does is reduce the catastrophic failure rate (PSUs fail a lot and having them outside the machine reduces down time), reduces noise since with less heat generated there's no internal fan and extends component lifetimes (less dust in the machines due to less reliance on air flow for cooling).

Tis doesn't really apply to the "dual 1GHz processor 1GB RAM, 4x30GB 10krpm SCSI" crowd, but for a lot of users, these smaller e-PCs are an attractive alternative, being more reliable and less intrusive.

Don't forget, though, that noisy PCs have other uses. In my case, any troublesome infants from visiting couples are ceremoniously placed in the computer room during dinner. Most pretty instantly fall asleep from the hypnotic noise of the fans!


The simplest answer ... (2)

trexl (16434) | more than 12 years ago | (#264035)

Most computers don't have External power supplies because they are Inside the case. This makes them Internal.

Glad I could help,

Seriously though, I don't think the components care where the power comes from, just as long as it gets it. They are most likely placed there because ideally computers should be self contained boxes ... who wants things dangling from them? Just a thought.

HO Scale (2)

sharkey (16670) | more than 12 years ago | (#264036)

Not sure it would be better. I remember the transformer for my train set giving off a much more irritating whine than a PC fan.


Re:IMHO (2)

meldroc (21783) | more than 12 years ago | (#264037)

Of all the lousy ways to save a nickel (literally when talking about mass-produced components), "wall wart" power supplies are the worst! How hard can it be to provide 3 feet of cord, plus a normal 3-prong plug, so you can plug the things in without blocking other outlets. Talk about cheap!

Re:Actually... (1)

mrzaph0d (25646) | more than 12 years ago | (#264038)

anyone else remember the early PC's that powered the monitor also? i remember when i dumped that one and got a new one i was quite disappointed to see that the new one wasn't like that, had to make room on my power strip for the monitor cable too. now it's normal.

Apple's G4 Cube (2)

rrwood (27261) | more than 12 years ago | (#264039)

The G4 Cube from Apple has an external power supply, for what that data point is worth. It looks okay, and the Cube is actually much cooler than I thought it would be. ("Cooler" not in the thermodynamic sense, though it is that too.) Coupled with one of those gorgeous flat panel displays, a Cube is pretty sweet.


Expense, and No Need For It (4)

scotpurl (28825) | more than 12 years ago | (#264040)

Few household appliances have external power supplies. The ones that do all draw very little power (radios, answering machines, ZIP drives).

I know PCs don't draw very much power, either, but if the power supply were external, you'd have to include special internal cables, a power socket (or two or three) on the case for these connectors, and some stylish, fancy case for the external power supply. All of which would drive up the cost of the machine $20 (which is a lot these days).

The real issue here is that Intel and the hardware manufacturers are deliberately picking case designs that require several fans to cool correctly. It's as if these engineers never heard of the word convection.

The answer? Buy a decent, quiet power supply [pcpowercooling.com] , and some cooling fans. Note that pcpowercooling.com has a new cooling fan that includes a thermistor. The fan spins only fast enough to keep cool, so it actually spins slower, and quieter, most of the time.

Most people don't care if they're going deaf from that little whirring noise, and OSHA's rules don't apply to the home....

Re:IMHO (2)

suraklin (28841) | more than 12 years ago | (#264041)

The Amiga 500 had a non wall wart external supply. Much like the G4 cube has now. I would like to see something like this with standard ATX cases. Cases could be made quite a bit smaller and easier to take to LAN parties.

Re:IMHO (2)

mayonaise (29272) | more than 12 years ago | (#264042)

You say that external power supplies are bad, but you didn't say why. I'm curious about this idea, so i'd like to know why they're bad. Substantiate your arguments, that's all I ask. =)

Re:no more dongles! (2)

jfunk (33224) | more than 12 years ago | (#264043)

Unfortunately, many of those devices have much different power requirements. Your DSL modem will probably need more voltage, and especially more current than your PIC board, because of the power requirements to drive the two data ports (ethernet and WAN).

I like the solutions for guitar pedals out there. My brother has one pedal that provides power to a bunch more. He only needs three or four wall warts (one for the pedals, one for the Ground Control, one for the DSP, and one for the digital recorder, if he's using it). Now he's obsessed with the Voodoo Pedal Power [voodoolab.com] but he wants to build his own with pots for simulating weak batteries, etc.

I really wish there were some standard for local DC power distribution. I envision a data-capable bus where a device could request the voltage it wants, so that the regulator wouldn't dissipate too much heat if it operated on 3.3V instead of 12V.

With something like that in my power supply, I'd be happy. Only X-10 stuff would waste space then.

Actually, that could be workable with existing equipment using small boxes on "legacy" devices... Sounds like a good application for a PIC12C508 for each device, with a PIC16Cxxx as the main power controller...

If anybody else is interested, feel free to email me. We could draft up something pretty quickly with this.

Re:It's a little more complex... (2)

CharlieG (34950) | more than 12 years ago | (#264044)

Your right - for the budget, you can't beat what's out there. Now, if you want to spend BUCKS, I can point you to some folks (Did I mention I used to work for a power supply company)

Re:It's a little more complex... (3)

CharlieG (34950) | more than 12 years ago | (#264045)

Not arguing your line loss figures, but you can always use a power supply with remote sense lines to make up for the line loss. I used to work in electronics, and we HAD to do it on some of our higher power boxes. When your pushing 120 amps of 5VDC with a +- 50mV spec, you have NO choice

No thanks. (2)

Stavr0 (35032) | more than 12 years ago | (#264046)

I got enough wall-warts humping each other dangling from my power bar PLUS two or three power bricks littered all over.

Re:It's a little more complex... (1)

bandgap (36365) | more than 12 years ago | (#264047)

Hi Charlie,

You're right, remote sense can correct for the drops. But then you have to face all of the output impedance / load transient issues that the bandwidth of the remote sense can't correct for. And that takes me back to my point that with enough $$ these problems could be overcome, but who would want to pay for it?

It's incredibly difficult to come up with a power system that can displace the $15-20 commodity power supplies that are in most computers. The commodity power business ranks up there as one of the more stressful ways to earn a living. They have razor thin profit margins with no room for error, with most errors resulting in either shock, fire, or smoke issues.


It's a little more complex... (5)

bandgap (36365) | more than 12 years ago | (#264048)

Wow, something on Slashdot I'm actually semi-qualified to answer! ( I used to design server-class power supplies)

There have been some good answers, but the biggest reason PC power supplies are internal rather than external boils down to $$. Well, that and safety, but then safety boils down to $$. And then technical, but that's also solved by $$.

There are at least four voltages produced by PC power supplies, with currents on the 5V line up around 12-20 Amps. The regulation of the 5V line measured on the motherboard is about +-5% or better (+-250mV), which at 20A would work out to about 0.012 Ohms of resistance split between cable and connectors. 14 guage wire (similar to an extension cord) has a resistance of 0.0026 Ohms per foot. So, about 5 feet of wire would chew up all of the allowed resistance with nothing left over for connectors. I've been loose with my numbers, but you get the idea.

Now imagine a cable from the power supply to the computer with 8-10 wires, all the size of those in a standard extension cord. Now, imagine paying for all of that copper.

The old AT-class and now the ATX class supplies are commodity products. This means that the design is stable, has been engineered and cost reduced to death, and are now being manufactured in low labor rate locations with component parts being negotiated to sub-fractional pennies.

Custom power supplies used to be priced in the $1 per watt range (in large volumes). PC power supplies are well down below the $0.10 per watt range and going lower. Anything new will have to survive being compared against a mature $15-20 solution.


Re:IMHO (3)

Tower (37395) | more than 12 years ago | (#264049)

Hmmm... I was envisioning more of the C-64 style of power supply (or the same thing found on many printers and some computer speaker sets). Standard 3-prong plug -> 2/4 ft of wire -> Fairly Large box -> 2-6 ft of wire -> power-hungry box. Lets you have control over the placement of the power converter, and doesn't use up any extra plug space. Wall warts are only good for low wattage apps. Wouldn't be all that nice for a 100-200W multi-voltage supply...


Actually... (4)

cr0sh (43134) | more than 12 years ago | (#264050)

As an owner of a A1200 (that's Amiga, folks), which had an external powersupply (actually, so did the A500, and A600), they SUCK! Why?

Trying to find a place for it was always a pain, because the cables came out front and rear. It was a nightmare. If it weren't for the location of my desk at the time, it could've been stepped on or tripped over. It was the only thing I hated about my A1200.

As far as noise is concerned, I doubt the fan in the power supply is noisy. I have a test setup right now with an ATX powersupply sitting out openly on my desk, and when it is on, it is all but inaudible. Even in a case, I doubt it it very loud (BTW - why all this talk about loudness? I don't mind the sound of computers - give me the thrum of a computer room A/C and powersupply system for company any day!).

I can only see one way having an external supply would be a good thing, and that would be if it had plugs for everything - no more wall warts, only one AC plug, everything else plugs into the powersupply. I am imagining something like a beefy looking power strip - it could even have a built in UPS for certain components. I would be even willing to bet the monitor could run off of such a system (maybe - I have a portable tube based TV that runs off a 12 volt/1 amp wall wart - of course, it has a small screen - maybe a larger monitor couldn't do it).

I would think you could actually build something like this yourself - getting large amperage bare power supplies isn't a big problem, so just build a case, add some custom cables... The only issues I can see you running into would be possibly noise (electrical) and voltage/current drops/sagging (from excess length of runs for the cables)...

Worldcom [worldcom.com] - Generation Duh!

Re:It's a little more complex... (2)

Dwonis (52652) | more than 12 years ago | (#264051)

most Pentium motherboards power the CPU with a switching regulator located right next to or even under the CPU socket. What about the 3.3v lines on the AGP socket (if there are any)? I hacked my AT power supply into an ATX one for a motherboard upgrade (saved me $100), and I had to set the 3.3v line myself. I'm beginning to think I didn't set it properly, and I've been having numerous, flaky problems trying to get AGP transfers working on both ATI and Voodoo3 cards. Sometimes it works, most of the time it hangs. So, my question is: does the motherboard regulate the 3.3v lines going to the AGP port? If not, could an incorrect voltage cause consistent X video performance, but kill 3D?

Re:most heat & noise from a P/S? Nope. (1)

3waygeek (58990) | more than 12 years ago | (#264052)

The general rule, at least according to the various overclocking sites that I've seen, is that the PS fan should blow out of the case, and that other case fans should blow in.

On my systems, I use mini or full tower cases, and I mount an inward-pointing auxilary fan on the lower front of the case (there's almost always a fan holder on the speaker mount or card holder cage). That way, cool air is drawn in from floor level, and once it gets heated up inside the case, it'll be blown out by the PS fan.

Re:IMHO (1)

3waygeek (58990) | more than 12 years ago | (#264053)

Would you settle for three? Target sells a 7-outlet strip with 4 normally-spaced outlets on one side, and 3 wide-spaced outlets, perfect for warts, on the other.

G4 Cube (4)

joe52 (74496) | more than 12 years ago | (#264054)

Doesn't Apple's G4 Cube have an external power supply? I assume that is part of how they managed to make the Cube so quiet (and so small).

Mine is (3)

polymath69 (94161) | more than 12 years ago | (#264055)

Back in the day, let me tell you, we had some powerful computers. Why, this here 486 DX2/66 was a serious processor, back in the day. Good enough for Windows NT, and still plays a respectable game of Doom from time to time.

So when this system was new, I gradually decked it out with one too many gadgets. Multiport serial boards, CD-ROMs, hard drives, tape drive, I don't know, but at some point it started needing more power than the dinky little supply in the mini-tower case could provide. And I couldn't find a supply with enough juice that would fit the enclosure.

So I got a big supply, set it on top of the case with the cover off, and ran the wires down to power the motherboard and all the rest. With a spot-fan on the CPU, no worries there, and nothing else gets hot enough to cause any trouble.

Maybe this approach wouldn't work on these newfangled, high-MHz, noise-sensitive systems they've got these days. Or maybe it wouldn't be a problem, as it isn't for me. Someone would have to try it.

Incidentally the system is still overpowered for what it does... it runs a dialup BBS and has a custom alarm clock from hell to get me up in the AM. (Wasn't that one of the apps CmdrTaco wanted in the BorgBox?)


Re:Mine is (2)

Xenex (97062) | more than 12 years ago | (#264056)

That brought a smile to my lips.

I'm reading this with Opera on a 486 DX2/66 with 32Meg of RAM running Windows NT 4 right now, and I have used it to play the occasional game of Doom against the Duron in the other room...

Re:G4 Cube (1)

MrHat (102062) | more than 12 years ago | (#264057)

No, it's not. I have one sitting right here, and I can assure you the power supply is external. It's a gray, rounded box, with the trademark Apple rapid-machine-gun-fire(tm) design on the sides and top.

Re:most heat & noise from a P/S? Nope. (2)

Trepalium (109107) | more than 12 years ago | (#264058)

I work at a company that sold some power supplies that sucked air in through the power supply into the case. The end result was the power supply ended up heating the air it was taking in, and then blowing it on the CPU which was much more heat sensitive. This, of course, made the power supply much more efficient at the expense of system stability. Most case fans these days blow air out the back of the PSU because the PSU tends to fail less often when things heat up than other components inside the average system. The general rule is you exhaust out the back of the case and PSU, and intake from the front and/or sides.

Re:most heat & noise from a P/S? Nope. (1)

giberti (110903) | more than 12 years ago | (#264059)

Um, my laptop doesn't have a fan on the power supply either (it has a small internal fan if it gets cooking) and is always quite (except for the CD Drive.)

There you have it, there is hope.

Re:most heat & noise from a P/S? Nope. (1)

pallex (126468) | more than 12 years ago | (#264060)

The amiga power supplies were cool in winter - one for each foot (if you had a A-590 hd).

It seems that often the fans are back to front - i believe its more optimal to have the air being sucked out of the case - if you have the fan pulling air in, then surely you are heating up that air in the psu, and passing it on to the other components?

Re:It's a little more complex... (5)

pallex (126468) | more than 12 years ago | (#264061)

"Wow, something on Slashdot I'm actually semi-qualified to answer! "

If only everyone here thought like that! :)

IMHO (1)

SpanishInquisition (127269) | more than 12 years ago | (#264062)

External power supply are bad, if you ever bought musical equipment (synth,effects, etc), most of them use external power supply and people curse at them. Some higher end model ( or older one) have the power supply built-in and you it's a real blessing when you find one. External power supply is probably the next step in the "cheapenization" of PCs, but it's really not more practical.

Re:Interfernece, cost (1)

stilwebm (129567) | more than 12 years ago | (#264064)

Right but that introduces cost. Not a huge cost, but enought that in a low-margin market people will avoid it. And the main intereference problem I'm talking about is running the wires from the power supply to the rest of the computer. You can shield it some too, but to remain felxible it is harder to shield it enough.

Interfernece, cost (4)

stilwebm (129567) | more than 12 years ago | (#264065)

Aside from power requirements of most modern expandable computers introducing the need for cooling, interference is an important factor.
When you have an internal power supply, the case shields against outside and emitted interference. You can shield the external power supply, but it is harder to effectively shield the multiple DC conductors that must go from the power supply to the PC. Inside the case, it is a much more controlled environment. This helps with stability a lot, considering components in modern PC's have to have over 1GHz of timing accuracy. Also, you don't have to make a cosmetically pleasing case for an internal power supply (unless your chasis is translucent), but you have to make it less than an eye-sore if it sits on the floor or desk. That extra casing introduces more costs.

Re:G4 Cube (4)

stilwebm (129567) | more than 12 years ago | (#264066)

Yes. It also uses convection to cool the CPU and other components. Since the Cube is small, they don't have to worry about users adding many internal peripherals to add more heat to the formula.

Re:most heat & noise from a P/S? Nope. (1)

de Selby (167520) | more than 12 years ago | (#264067)

I don't have a CPU fan and my hard drives are silent. An external power supply would be good for me. (Or a pcpowerandcooling supply, but that's expensiove...)

Re:Interfernece, cost (1)

bacchus612 (168559) | more than 12 years ago | (#264068)

Ever looked at how thick the case of you pc is? It doesn't take a lot of metal to properly shield from electromagnetic interference (from both directions), for that matter, it doesn't even take too much shielding to guard against EMP. My point is, the power supply's casing wouldn't have to be made of plastic.

Clustering/Rackmounting (4)

bacchus612 (168559) | more than 12 years ago | (#264070)

The main reason _I_ would like an external power supply is for my server rack (in progress). I've got 5 pcs in rackmount cases (of varying sizes), they're all watercooled (read: NO fans at all in the cases except for the powersupply). Now, if I could buy a 1 or 2-u powersupply that would run that many boxes (and preferably be designed for watercooling itself - I can dream can't I ;) I'd be in heaven. If we had external power supplies for desktops, there would already be some type of standard (hopefully) connector. Thus, large capacity PS's could be designed with a little scalability in mind (picture a power hub with multiple ports).

A hardware hacker's dream (1)

psicic (171000) | more than 12 years ago | (#264071)

If the external power supplies were well designed , then I'm all for the idea. Having had a vast array of old computers, including some like my A600 which has an external power supply, I can say that design makes all the difference. A box with a wire coming out each end may not sound bad, but unless it has a long cable, it can be a nightmare to place. (I would suggest the 'input' wire and 'output' wire be on the same side of the adaptor). It would also need to be well weighted or securable - the A600 power supply was constanly being tipped over everytime the cable jiggled - in the end I used big wads of blue-tack to keep it in place.
The idea of one standardised external power supply shouldn't be dismissed so readily. It could end all this hassle with so many different connector types on laptops - if there was a standard for desktops and towers, laptops would surely follow. As anyone who has ever picked up a cheap second-hand laptop - invariably with a dead or dying battery and no ac adaptor - knows, it can be hell first tracking down the right type for your model, then actually finding an example for less than £100. And let's not forget it would also either allow a reduction in PC case sizes or else leave a good chunk of room inside the case for extra add-ons. As anyone that likes to mess about with old x86s and Pentiums, a few centimetres can make all the difference in what you can do with the case on and the case off.
I like the thinking of others here that seems to have spread to the idea of having an external power supply that can power many machines at once....that would be sweet! I'd no longer have to have a daisy chain of surge protected extension chords stretching from every power socket in my house. I wouldn't have to keep changing plugs(buy as many six socket extension chords as you want, you'll always run out of space). It would be great! If it weren't for the fact I've spent all my money on extension chords, I'd be first in line to buy a PC with external power supply. (That, and the fact I could have a fairly good go at hacking one together myself....maybe)


Re:Cost? (1)

Gordonjcp (186804) | more than 12 years ago | (#264072)

I think they're only that expensive because they come in a nice box with the manufacturer's logo on it. If you bought a "surplus" psu from a company that deals in "reclaimed" bits, Display Electronics springs to mind, you'd get a 12v/5v psu that you could use as a MIG welder for about 20 quid.

Extension cords! (5)

billcopc (196330) | more than 12 years ago | (#264073)

Why not attack it the redneck way ? Just buy a truckload of molex extensions and chain them together until you have about 12ft of unshielded power wires dangling around.. that way you could hide the case away and screw the cdroms and tape drives directly onto your desk thanks to the extra long power connections.. as a bonus it will automatically kill your roommate's cat in seconds as soon as it sinks its teeth into it.

External power supplies cause interference (2)

Cerlyn (202990) | more than 12 years ago | (#264075)

Unfortunately, power is not the only thing that rides on a power cord. Keep in mind that you have components operating anywhere between 100 MHz and 1 GHz inside of a computer. Given FM radio is from about 85-108 MHz, UHF TV around 500 MHz, your 900 MHz cordless phones, etc., one sees that all you need to get a computer to cause interference is an antenna that takes said signal outside of the shielding metal case. What better way is there to get a signal out of a computer than a power cable? After all, 50/60 Hz cables were never designed to keep 100 MHz+ signals contained.

Granted, you can fight this noise by using shielded cables, bypass capacitors, etc., but adding components comes at a cost. Do you really want the extra cost of shielding power cables/connectors & RFI that made it into the power supply?

This reminds me of story (I don't know if it's true or not). First, they build your US $100+ priced power supply, and call it Class A. Then they take out a few components (a few dollars worth), see if it works, and call it Class B (aroud $30-50). Then they take out a few more, and call it Class C ($15) if it still operates. Most computers have Class C supplies. No wonder bad or unstable power supplies are the cause of so many failures.

Re:most heat & noise from a P/S? Nope. (1)

Vassily Overveight (211619) | more than 12 years ago | (#264076)

and most noise, believe it or not, is generated from those cruddy little CPU fans.

Unless you're one of those nuts (ahem) who wants to put the biggest, baddest hard drive available in his computer. Adding my 75Gb DeskStar made my computer go from "is that thing turned on?" to "Hey, something's making a horrible racket in the next room."

External supply doesn't just have to be for the PC (2)

MadCow42 (243108) | more than 12 years ago | (#264077)

If you're going to bother moving the power supply to outside the case, there's no reason you can't have additional connectors to suck other CD voltages from for your scanner/zip/modem/etc.

I'm sure that one (big / 300w+)external DC supply is a lot more efficient (and cheaper) than an internal one plus 6 wall-warts for accessories...

The problem is that you'd either have to choose a standard connector type for each voltage, or have some auto-sensing system...


The minute ext pwr supplys exist, more bitching... (1)

Blaede (266638) | more than 12 years ago | (#264078)

...will start. People will start complaining about how it takes up space, there's another long cord to trip over, blah blah blah. Give people what they want, and they will gripe about it.

Re:Actually... (2)

markmoss (301064) | more than 12 years ago | (#264079)

The problem with the pass-through AC jack was that it usually had a quite limited current capacity -- it was OK for the tiny little monochrome monitors, but the early VGA monitors would overload it so they always came with standard cords to go straight to the power strip.

Re:It's a little more complex... (2)

markmoss (301064) | more than 12 years ago | (#264080)

I don't know in general. We build a customized motherboard, made to fit inside of a particular machine, with special ports to read a keypad and to control the machine, but it still has the standard stuff too. In the 233MHZ version, two on-board regulators are required; one of them provides a particular voltage for the Intel CPU core, the other 3.3V for the CPU I/O circuits and the chipset. But this design was contracted out to a company that had expertise in PC motherboards; we usually do this for anything over 10MHz, which still leaves a lot of low to medium power embedded controller work for us.

Re:It's a little more complex... (5)

markmoss (301064) | more than 12 years ago | (#264081)

Correct, for a given power the current is inversely proportional to voltage, so bringing in the power at 5V instead of 120V takes thick, expensive, and unwieldy wires. I think this arrangement wouldn't make much sense unless the wires were about 5 feet long so you could put the supply on the floor -- if it has to sit next to the mainframe, you've just added more clutter. With a separate case and fan you've added $10-15 to the parts cost of the system, or $20-30 to the street price.

The other thing is, a long distance between the regulator and the load slows down the response to load variations and degrades the voltage regulation no matter how thick the wires are. High-speed rack-mounted electronics systems often put a regulator on each circuit card, with power distributed at an intermediate voltage, just to get the regulators a couple of feet closer to the loads. It might make sense to do this with PC's -- convert AC to 48 and 12VDC in a separate module, then put simple switching regulators on the motherboard to transform 48VDC to +5, +3.3, and whatever other voltages are needed. One part of this is already in place; most Pentium motherboards power the CPU with a switching regulator located right next to or even under the CPU socket.

You don't mean dongle (3)

Spamalamadingdong (323207) | more than 12 years ago | (#264082)

The technical term for the little transformer built into a plug (so you can only get one into a wall outlet, or half as many on your power strip as it has outlets) is "wall wart". Their efficiency is often hideously low, and it's a pity that there aren't Federal regulations restricting how much power they're allowed to waste (especially when the device they are powering is in the off or standby state).
spam spam spam spam spam spam
No one expects the Spammish Repetition!

powered USB/FireWire (2)

janpod66 (323734) | more than 12 years ago | (#264083)

I think the PC case is a pretty good place for a power supply. But many peripherals could be powered through their data cables; both USB and FireWire offer that choice. Unfortunately, making anything low power tends to make it more expensive, so the cheap stuff will likely continue to come with its own separate power supplies.

Re:You don't mean dongle (1)

jonniesmokes (323978) | more than 12 years ago | (#264084)

Wall wart = dongle in my old lab

ofcourse dongle is far more useful of
a word 'cause it can be a derogatory
word for anything that plugs-in, such
as an evil copy-protection dongle;
those pesky devices which stick off
of parallel ports and let expensive
applications run.

I will however admit that in this case
wall-wart is a wonderful word and I
should've remembered it.

And they should make those things illegal.
However, people love peripherals and
peripheral makers hate UL/CSA/FM listing
120VAC devices.

Re:no more dongles! (1)

jonniesmokes (323978) | more than 12 years ago | (#264085)

I think you may have a point here. I kinda
would like to draft up something. I'm not
a member of the IEEE or anything, but perhaps
we could even send in something to them

no more dongles! (5)

jonniesmokes (323978) | more than 12 years ago | (#264086)

I can't say I want anymore power supply devices lying around my desk. So please don't suggest that they make another. Its wonderful and unusual that they make proper UL listed power supplies for computers. Most cheap things don't want to plug into the wall. Currently, I have One AC-DC for the scanner One AC-DC for the external zip drive One AC-AC for the DSL modem One AC-DC for the PIC16F873 board These dongles either take up cumbersome space or they take up way too much space on the powerstips. Happily the printer, monitor, and computer all plug in normally. On the other hand... If they could link all of these peripherals up to the same power supply, that'd be pretty cool. I wouldn't mind having just one external power supply if we could plug all the devices into that. Unfortunately daisy chaining is frowned upon in DC power supply situations. So that means a spidery nest of power cables no matter what we do. Is there anyway out of this? How about a tesla-coil right above the computer ;) I'd give mega frankenstein points to anyone who made a working computer system using a tesla-coil.

Re:most heat & noise from a P/S? Nope. (1)

astapleton (324242) | more than 12 years ago | (#264087)

It should be a simple case (pardon the pun) of redesigning PC cases and power supplies. An externally-mounted power supply that literally 'plugs into' external power connectors that are in turn connected to interior wiring for internal devices, including switches, LEDS, drives, motherboards and their various capabilities, as well as a case-mounted fan that's part of the case, not the P/S. That way, users can buy a case with or w/o fan and with or w/o external power supply. Chassis and P/S manufacturers should go nuts over this idea...charge $100 for the complete set, or charge a little higher for the components seperately and make more money on the same set in pieces...and buyers will think they're getting a deal. Wish I knew some engineers who were willing to share the profits with me.

Standardisation of External Power Sources (1)

BigLug (411125) | more than 12 years ago | (#264088)

Why does everything with an external power supply come with its own supply?

Seems to me (and also to Douglas Adams - Author of Hitchhikers Guide etc [see here [douglasadams.com] ]) that it would be much better to wire houses with extra sockets on the powerpoints - thus the point will have (for example) a 250vac, a 5vdc and a 12vdc socket. Then every manufacturer creates their products to work using these sockets and thus you dont have to own 1000 'dongly things' .

There will be some equipment (your PC may be one of them) that would need to do its own conversions - maybe for getting a 0vdc or some such - I'm no expert. But for the most part there would be no need for damned power supplies for everything!

Re:Clustering/Rackmounting (1)

hoggoth (414195) | more than 12 years ago | (#264089)

I tried watercooling my PC, but I got all kinds of sparks and fried the motherboard.

I think I used too much water.
Next time I'll just pour a little bit at a time.
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