Atomic I/O letters column #53
Originally published in Atomic: Maximum Power Computing Reprinted here January 2006.Last modified 16-Jan-2015.
Power pickle
Onboard sound has been a bit below par recently, but MSI put a Creative chip on their newer boards, which is great news.
The K8N motherboard family has a power supply issue, though, as quoted from their Web site: "For this model, you must use a Power Supply which has a -5V pin supply." Without the -5V rail, the onboard sound won't work.
This -5V rail is not included on many newer 24 pin power supplies. What power supply will work?
Ben
The -5V rail isn't quite dead.
Answer:
The -5V rail dropped out of the ATX spec a while
ago, and now a lot of big-brand PSUs either don't have that white wire going to their main connector at all, or don't
have anything connected to it.
You can still find PSUs with -5V rails, though. Various Topower models, for instance, are available here in Australia, and have -5V - The 450P5 and 500P5, for instance. They've got 20-pin connectors, but some come with a 24 pin adapter.
You can plug a 20-pin ATX connector straight into a 24-pin EPS12V socket, too; the four pin-holes you leave empty are an extension of the ATX12V idea, and just duplicate other rails to give lower resistance. If the PSU's grunty enough, such a setup should work OK.
Various Topowers have more than adequate ratings for current PCs, and the shinier ones have trim-pots for the high current rails, so you can goose them up a tad if higher cable resistance robs you of a few tenths of a volt.
Settling hash
I was reading a piece on game integrity checking in a past issue of Atomic, and have a question regarding the use of MD5 in integrity checking. Why couldn't games run a check each time you started the game to find out if the game is illegally patched, with NoCD patches and the like?
Sam
Answer:
First up, it's highly questionable whether no-CD patches are, themselves, in any way illegal. Laws like the US
Digital Millennium Copyright Act make
it expressly and criminally illegal (as opposed to a mere breach of contract, which is a
civil matter) to circumvent copy control technology,
no matter how lame that technology is, and even
if you're only doing it so you can do something else that's perfectly legal.
Like, for instance, run the game you bought on your subnotebook, when you've swapped out the CD-ROM drive for a spare battery.
Australia can expect to enjoy DMCA-like laws as well, as part of our recent Free Trade Agreement with the USA, but that doesn't mean they'll stand up in court. Such laws, and various provisions of End User License Agreements, can prohibit all sorts of things that may in fact be found by the courts to be perfectly fine. Or the laws may simply not be enforced. Remember, in Australia it's still technically illegal to record most TV shows with a VCR. The jails aren't exactly packed with offenders, though, and the law may finally be about to change.
Getting to your actual question: Yes, hash functions of various kinds have been used by game makers to stop people patching games. This isn't just a copy-control issue; verifying that the game files haven't been changed is also a good way to slow down cheaters.
Simple MD5 authentication, though, doesn't work very well. Even if you ask for an MD5 hash of some randomly chosen portion of some randomly chosen file every five minutes, all a patched game executable has to do is keep copies of all of the original files, and run the hashing algorithm on those.
If you want to learn more about the continuing arms race between cheaters and decent upstanding folk, try starting here and here.
Shortophobia
At the moment I'm aspiring to create a custom case for my computer. I'm thinking of using some form of sheet metal.
In designing the case I remembered a mIRC log I once saw of someone that plated their case with copper. Upon turning the computer on, the fuses blew in the house and fried the power supply.
Is there any truth in this story? If the case is made from a conductive material, will damage result to the electrical components? I need a definite answer before I start causing pretty little arcing effects in my experimental case.
David
Answer:
If you screw up construction of your computer so badly that you short the incoming mains connector, then yes, you'll
blow your house fuses. Perhaps whatever you did to achieve that will also thork the PSU.
If you just short the PSU outputs, though - which should be all you can do, if you haven't been mucking about inside the power supply - then only the PSU's fuse will pop, and that'll be that.
Also, virtually every computer case is made from a conductive material. Most cases are steel, which isn't what you'd call an insulator. It only conducts electricity about a quarter as well as aluminium - which is what telegraph pole power cables are made from, because its conductivity-to-weight ratio is better than copper's - but steel is still more than good enough to short stuff out. The insulative paint is on the outside.
And, of course, some computer cases are made from aluminium. Some of them have non-conductive anodised coatings all over; most don't.
The conductive casing is earthed, and connected to the grounds of the components inside. That way, it acts as a radio frequency interference shield. The classic rookie mistake of not using motherboard standoffs, or of putting standoffs in places where the motherboard doesn't have mounting holes, is a great way to connect all sorts of other things to the casing.
So don't do that.
D-shaped plug, cross-shaped hole...
I recently got a new laptop - an Acer Ferrari 3400. Nice piece of kit, cheap, but rather fast (if a little hot). I also got from work, a new Sun 19 inch LCD flat panel display (I believe they're actually made by Samsung). This has two inputs - standard VGA, and DVI-D.
Now here is the problem - the ATI Radeon Mobility 9700 on this laptop has only VGA out. Of course that connects to the LCD screen with no problem, but I'd really like to make use of the DVI part.
Having done a little research, I understand that there are three types of DVI connector - DVI-A, DVI-D and DVI-I, where by -A is an analogue input, -D is digital, and -I is integrated, supporting both A and D. I've also seen that you can buy dongles that will convert a VGA D-Sub interface to DVI. But I suspect that wouldn't work in my case, as the analogue signal needs to be converted to digital.
I've seen converters around the Web that sort of do this, but they're expensive and seem to be more aimed at projection requirements.
Will a simple conversion dongle work, or am I right in my assumption that it won't work, and an additional analogue to digital converter would be needed?
Chris
Answer:
Yes, you're right. All the cheap adapter plugs do is connect the appropriate pins on the VGA connector to the analogue
RGB pins on a DVI-I socket.
(The analogue pins are the cross-shaped arrangement on the right side of the DVI-I socket, when you look at it with its narrow side downwards; they're therefore on the left side of the matching plug.)
By definition, an actual video format converter won't give you any better quality than you'd get by using straight VGA. Actually, you'll lose a little image quality, and there might be refresh rate weirdness as well.
The converters are just so you can connect something with a VGA output to something that only has digital DVI input. The setup you're using already is the best you're going to get (and, actually, will probably look just as good as if your laptop had a digital DVI output).
I've written about DVI issues in the past here, here, here and here.
100BaseT audio
I was wondering what you think about using Category 5 network cable as cheap DIY speaker cable?
Do you think it might work?
Will
Answer:
Would it work? Sure. Would it sound any better than any other speaker cable of reasonable diameter? Nope.
This design is, presumably, based on some idea about induction or capacitance or skin effect or something, making the usual audiophile mistake of assuming that things that happen in the megahertz (or gigahertz...) range also happen to audio frequencies.
This stuff's been chewed over at very great length by people who know little about electronics, and at far lesser length by people who do and who can therefore rule it out as irrelevant and move on.
Better people spend time doing macramé with computer cables than spend zillions of dollars on snake oil wires from voodoo salesmen, though.
Do not look into projector with remaining eye
I've read a lot of articles about projectors, but what about colour laser projectors? They've been around for a few years. Always in focus, almost unlimited screen size!
I would have thought it would catch on, but it didn't.
It's all because of some secret government plot, I tell ya!
Danny
Answer:
Colorvision's current products look very impressive.
Unfortunately, no progress seems to have been made in getting these things down out of the $US100,000 price and refrigerator size classes. The scanner hardware in them (super-fast polygonal mirrors and/or badass DSP gear) is probably the big obstacle; blue diode lasers of reasonable brightness (as opposed to the 10-watt-plus lasers in the big projectors, which're far too powerful for home use) are also a problem at the moment.
A simple laser projector would also give a strange twinkly image, thanks to "laser speckle", caused by the laser light not being absolutely perfectly in phase. You can see the same speckle in a laser pointer dot. Either the big manufacturers have a solution for this, or it just isn't noticeable on a huge screen at a large distance.
Vanishing URLs
When a Web site times out in Firefox, you get a stupid pop-up error box, and a blank browser window with nothing in the URL bar, so you can't easily retry the request.
There doesn't seem to be an extension that fixes this. Can it be done?
Kevin
Answer:
Yes, it can.
Type "about:config" into the address bar, type "error" into the Filter box above the big list of config options, and you should be left with only the "browser.xul.error_pages.enabled" option visible. Double-click it to set the value to "true", and your problem will be solved.
Firefox 1.5, by the way, has this feature turned on by default. It also has a prettier error page, to soothe your troubled soul.
