Dan's Data letters #89
Publication date: 6 February 2004. Last modified 03-Dec-2011.
The joy of brand-name PCs
About a month and a half ago, a friend dropped off an old-stock HP Pavilion 8380 with a hundred dollars US, asking me to install XP and upgrade the system as I saw fit. So I bought three sticks of this PC133 RAM.
HP's site says the 8380 will support three 128Mb sticks of PC100. The RAM I bought is PC133 (because it was cheaper than the PC100), since I have always read that PC133 will downclock to 100MHz when put in that type of slot.
Long story short, the PC is not happy when the new RAM is in. Initially, XP was crashing during startup (not finding ntkernel.sys, and one other error I can't remember right now). However, now it won't boot at all (or at least it doesn't give any video output when the new RAM is in) when I turn the system on. When I put the old RAM back in, the box boots into XP just fine; and I know the RAM is good, because I'm using it in another box to write to you. I also put in an old 64Mb PC100 stick that I pulled out of an old Presario, and got the same results.
So, I'm stuck. Any input you could offer would be most appreciated.
Craig
Answer:
You're quite right that, generally, over-rated RAM is not a problem. Some
laptops won't work if you give them RAM with a higher speed rating
than they expect (the RAM would work if only they could figure out
what it was, but they can't), but most desktop systems are fine with faster
RAM.
Some, however, aren't, and I think the 8300-series Pavilions are in this category. They want PC100, not anything else. This is unusual for a system using the BX chipset, but it seems to be the case.
Then again, the crucial.com memory selector suggests two PC100 modules and one PC133 one for the 8380, so I don't know what the deal is. The selector also says this system needs special RAM, so either it means PC100 and the PC133 module is a mistake, or it's talking about a single/double banked memory issue.
Your dirt cheap PC133 RAM probably isn't very exciting stuff, and the three modules might have problems working together at the best of times - but one module would definitely work by itself, if the motherboard didn't have a problem with the RAM type. So I'm betting it is a mobo issue.
Buy more expensive memory from crucial.com, or anyone else that'll guarantee you the memory will work in this system, and you'll be fine. If you've got a competent local computer store, cart the 8380 up there and have them stick some RAM in it while you have lunch or something; that'll save you from mailing back dud memory.
Audio video!
Some time ago a friend of mine purchased a basic composite-output CCD (or quite possibly CMOS) board video camera. Brand unknown, his for not much from eBay. I've recently been looking into MP3 players and the one my fancy alighted upon, the iRiver iHP-120, has onboard analog inputs.
My bad idea lobe immediately suggested that a simple adapter ought, in theory, to allow me to connect the composite output from a cheap CMOS board camera to the line-in on said MP3 player. A mono sound channel could presumably be kludged into the second channel in the stereo line-in. It seems as though it's all just arbitrary analog waveforms, which should be captured and reproduced with something at least similar to adequacy by any decent audio hardware, right?
Here is where the question comes in: I've looked at various references on the subject; but have been unable to answer the question "will I do something unpleasantly expensive to one or more of the components by doing this?" I realize that this setup will have ghastly limitations even if it works, but I'm willing to take a risk on the concept as long as I'm not likely to actually break anything. Are there any especially nasty pitfalls that you can see in this scheme?
John
Answer:
You could connect it and give it a try without hurting anything (there might
be an impedance mismatch, but it wouldn't do any harm) - but it wouldn't
work worth a damn.
Composite video has a bandwidth of about six megahertz; even CD quality audio only manages a bit more than 20 kilohertz.
(Lossy audio compression of a non-audio signal, by the way, would also do very strange things - I remember seeing a site with some MP3 compressed-and-uncompressed image files on it, but I can't recall where now. I had faith that a reader would tell me where it was; it took four years, but someone just did!.)
It's possible to fit some kind of video onto formats that were meant for audio, as with the old Fisher-Price Pixelvision camera I mentioned in Letters #79 and the marvelously nutty VinylVideo. There's no way you can squish a whole real time composite signal onto a 20KHz-odd-bandwidth storage medium, though; you'd have to pre-process it down massively if you wanted to get anything vaguely recognisable out of the other end.
Radeon starvation
I'm getting a Radeon 9800 Pro, and it requires a 12V direct hookup to the PSU, and says the minimum requirement for the PSU is 300 watts. I only have a 250W PSU. Could this damage anything, would it just not run, or could it only maybe cause some problems?
Brandon
Answer:
If there's a problem (which there may well be - a decent 300W PSU is enough
to run pretty much all PCs, as I've said before,
but 250W is stretching it), it'll just be flakiness when you run 3D applications.
If you don't plug a high end Radeon's extra power lead in at all it'll give you an aggrieved text-mode message on system startup, and it'd probably do the same if its power supply was miserably far away from 12 volts, which it might be if the PSU was severely overworked. You'd be much more likely to just get crashes in games, though.
1.2 * 3 = 7.3?
I'm about to buy my first digital camera tomorrow, (Nikon Coolpix 2100), and was all set to go with NiMH AA cells and a Maha C401FS, but then I noticed that you can now buy rechargeable CR-V3 batteries. Info on them is scarce though. What do you think about them? Here is a review and a sales page.
Emil
Answer:
I don't think the numbers in the Steve's Digicams
review
add up. The rechargeable CR-V3s have a capacity of only 1200 milliamp-hours
(not mentioned in the review, but mentioned on the
product page it links to). Taking their nominal 3V rating into account,
that's 3.6 watt-hours.
1800mAh capacity NiMH AA cells are now commonly available, and 2000mAh and higher cells exist. A pair of 1800mAh, 1.2 volt AAs have 4.32 watt-hours of combined capacity.
And yet, according to the Steve's Digicams page, you can only expect 250 photos per charge for NiMH cells (of unspecified capacity...), but 420 from the (presumably lower capacity) CR-V3.
Your camera would have to work a lot worse from 2.4V instead of 3V nominal for this to be the case.
The Thomas Distributing page lists the RCR-V3 capacity as only 1160mAh, but says it'll outperform a 2300mAh NiMH (presumably a pair of them).
I don't see how that can be the case. OK, the lithium ion batteries will hold their charge over time much better than NiMH cells, which is a big plus for cameras that sit on the shelf unused for months. If that doesn't matter to you, though, then the more-than-$US30 price for one RCR-V3, along with the implausible claims, makes them very unappealing.
Emanation explanation?
I refer you to the discussion here.
Creative's Nomad Jukebox Zen uses a 2.5 inch hard disk. Do you think this incident could possibly have been caused by magnetism? Seems most improbable to me since you mentioned that even NIB magnets sitting on top of an exposed HD will not harm the HD, but does this hold true for 2.5 and 1.8 inch drives and even Microdrives?
Joseph
Answer:
Nope. The coercivity of small hard drive platters is the same as that for
larger platters - a few thousand Oersteds, so you need a field of at least
a few thousand Gauss to demagnetise them. If you sat a big nasty rare earth
magnet (like the giant cylinders or pyramid I checked
out recently) on top of a laptop drive then you might be able to wreck
it; there's not much space between the casing and the platter in a super-slim
drive like that. The pyramid magnet, with its 7000 Gauss surface field strength
at the pointier end, might even be able to damage data on a desktop drive.
But field strength falls off approximately with the cube of the distance;
no loudspeaker has an external field anywhere near strong enough to damage
data on any hard drive.
Loudspeakers don't have large rare earth magnets in them, anyway. Rare earth magnets may be used for smaller drivers, but the big magnets on pretty much all big bass drivers are still cheap, lower strength ferrites.
Also, if the drive had been magnetically scrambled, I think the basic filesystem and probably also its servo tracks would have been scrambled too. The player would probably have been a paperweight, and certainly wouldn't have been recoverable by just deleting and replacing the contents.
Phosphor stacking
I've heard it said, often, that white LEDs are really just blue ones with a phosphor layer on them. Considering CRT monitors also contain a phosphor layer, I've noticed that when you shine a white LED light at a CRT computer screen the reflection of the LED you see in the screen is in fact blue. Is there a scientific explanation as to why?
Liam
Answer:
Yes, white LEDs are just Blue LEDs With More; this is why the light
from white LEDs is often quite blue-white, and why it's often more
blue in some part of the beam (the middle, the edge...) than in others.
The CRT-phosphor thing, though, isn't true. Well, it's sometimes true, but not because of the monitor phosphor.
The phosphor on computer and TV screens is mildly sensitive to external light; sit in front of a CRT in a darkened room, preferably when your eyes are adjusted to the darkness, then close your eyes, turn on a flashlight, and "doodle" on the screen with it. Turn the flashlight off and immediately open your eyes again and you'll clearly see the dying ghost of what you "drew".
That's where it stops, though. If things look blue reflected in your CRT, that's probably because of its anti-reflective coating, which is eating other wavelengths of incident light (and, cunningly, letting through all visible wavelengths from the other side of the glass).
Not all monitors have a coating that works like that. Some give reflections of other colours, or no particular colour tint to reflections at all.
Also, do not expose to fire or flame
I have purchased a nifty 15.6V cordless drill with a flashlight, 2 NiCd batteries, "dumb" charger, and a carrying case.
The manual warns me that I am not to store the batteries in the tools. But otherwise, the tools will not fit into the carrying case. What to do?
Ordinarily, I will use the drill at least once a week, since it is very useful. The flashlight, not as much. Why shouldn't I store the batteries in the tools, and for what period of time?
James
Answer:
Ignore the warning*. Store the batteries in the tools.
* Dan's Data disclaims all responsibility in the event that any advice rendered should result in house fires, the eruption of boils or pursuit by slavering abominations from beyond time.
I'm not sure what the reasoning behind the warning is. The batteries for a lot of cheap cordless tools have pretty horrifyingly fast self-discharge (charge them, leave them a month, and you'll have close to no charge left) but it makes no difference whether you leave them in the tool or on the shelf - they may self-discharge a bit slower if you store them in the fridge, but the difference won't be amazing, and you'll need to warm them up again before they'll give you full capacity anyway.
I can think of no reason why leaving the batteries in the tools would present any particular hazard, assuming nobody drops a piano on the drill, or something. Leave the battery in there with confidence.
Saturday at f/8?
After reading your piece on digital photography I started hunting around for a decent digital camera. The Fuji FinePix S5000 interested me, but the maximum exposure time is 2 seconds. If I want to do some macro work, is this going to limit what the camera can do?
Guy
Answer:
Not very much. Because this is a small-sensor camera with a maximum F-stop
of f/9 (like most consumer and prosumer digicams, as I explain on the
first page of my photo tutorial), it throws
a much brighter image per unit area of sensor than a large-sensor camera
like a DSLR will.
You still won't be able to do minimum-aperture macro work by ordinary indoor night-time light, but a couple of cheap hardware-store floodlights and gimcrack reflectors to match (if you don't have a low white ceiling) should be more than enough to bring exposure times down well below one second. Just one 500W flood might be adequate, but it's nice to have a couple so you can angle them differently to fill in shadows.
The exposure calculator here can be used to get a ballpark idea of the exposure times at a given aperture, for different lighting conditions. Hardware-store floods can easily get you up to overcast-daylight light levels.
Real medical magnets
My daughter has a vagus nerve stimulator implanted in her shoulder. It is activated by a magnet. The two magnets they gave us are too large for her to wear on her wrist. Do you know of any 50 - 70 Gauss magnets suitable for attaching to a bracelet?
Peter
Answer:
There are lots of small-ish NIB magnets that might work, but it depends
how deeply the reed switch (or whatever switch the stimulator uses) is embedded.
Small magnets have rapid field strength fall-off over short distances; right
next to the magnet surface the field strength may be close to 100 times
what's needed to activate the switch, but a couple of centimetres away it
won't cut it.
If you know how deep the switch is (presumably your daughter's doctor can tell you) then you could work out what kind of magnet you need, and ask a custom-magnets place like Engineered Concepts what they recommend. Engineered Concepts handle odd magnet enquiries all the time.
Alternatively, you could buy a grab-bag of cheap NIB magnets like the ones Forcefield sell and just see if one works.
If none do, you've still got a bunch of magnets to play with!
Better than a Roomba
Have you put your name down for a NS-5 yet? or are you waiting for the female version?
Shaun
Answer:
I presume Fox (the "I, Robot"
movie company) have reached an agreement with
iRobot Corporation regarding branding
issues.
The NS-5 is, of course, not an actual product - well, not for another 31 years, anyway!
