[HN Gopher] Casio-F-91W die-shot
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Casio-F-91W die-shot
Author : picture
Score : 155 points
Date : 2023-01-01 19:41 UTC (3 hours ago)
(HTM) web link (zeptobars.com)
(TXT) w3m dump (zeptobars.com)
| vasqw wrote:
| I bought one of those recently and I was surprised by how
| inaccurate it was. It drifted like 15 seconds every month. From
| what I've been reading, that is normal, but I was surprised -
| with all the technological advances that we have it is odd to
| think that cheap timekeeping is not a solved problem yet!
|
| Also: how is the software of these watches without a CPU
| designed? Is it something like Verilog or whatever?
| jimmyjazz14 wrote:
| Citizen has a quartz movement that is rated to only drift plus
| or minus 5 seconds a YEAR which is quite impressive though they
| cost around 2000 dollars and are exclusive to the Japanese
| market. Several other brands out there make high accuracy
| quartz movements (which is done with thermal compensation) but
| they do generally cost more than cheap Casios.
| Tor3 wrote:
| At around 1976-1977 I bought one of those fancy new LED
| wristwatches, where you pressed a button and the time lit up in
| red. Straight out of James Bond, as I recall.
|
| As I was studying electronics at the time I brought the watch
| to the lab and opened it and connected a frequency counter to
| the oscillator, you could clearly see the crystal and a little
| trimming pot (I don't remember by now if that was a pot or
| something else - capacitor maybe), and adjusted it to exactly
| 32768Hz.
|
| After that the watch drifted less than one second per month,
| and it kept the stability for the rest of the year (until a
| bicycle accident which resulted in a smashed watch).
|
| I've never since owned a watch which was even close to that.
| They're drifting so much that I can't even rely on my watch to
| catch the bus (there's a stop outside my home and the bus is
| there exactly on time).
| hotpotamus wrote:
| Citizen has a movement where they throw all the tech they have
| at it to guarantee 1 second per year accuracy. I remember
| things like quartz crystals have aging effects, so they used
| pre-aged crystals - little details like that. It even has an
| anti backlash mechanism on the second hand so that it ticks
| perfectly with no visible wobble. It probably doesn't make
| sense when it would be much cheaper to just use an external
| radio/GPS time source, but as a watch company, it makes a
| statement about their craft.
|
| There are other high-accuracy watches (it's mostly a Japanese
| market thing), and I believe +/- 10 seconds a year is
| considered fairly pedestrian in that world.
| _ph_ wrote:
| Almost all quartz watches have a similiar movement, running of
| a 32kHz crystal. Those give you about 15s/month accuracy, which
| is an oder of magnitude better than most mechanical watches and
| that for a very few bucks. More precise quartz watches exists,
| but they require quite a bit more effort, which of course
| translates into costs.
|
| Actually one of the earliest quartz watches on the market from
| Omega used a 2MHz crystal and was very accurate. Personally I
| own a Seiko with a 200kHz system, which is good for about
| 20s/year. Then there are the thermo stabilized systems, which
| are even more accuarate. The problem is, that the frequency of
| the crystal depends on its temperature which is the main source
| of time inaccuracy (there are some watch enthusiasts which do
| get egg breeding cupboards which have constant temperatures up
| to tenths of degrees, they make for very accurate watches).
|
| Currently, the best movements on the market are accurate to
| about 5s/year, which is pretty amazing considering the watches
| are worn on your wrist in varying conditions. With my precise
| Seiko watch I could even notice a slight change in speed when I
| moved quite a distance to a different town with slightly
| different weather. That shows how big a challenge a really
| accuarate wrist watch is.
|
| Then there are the market concerns. The most basic and cheap
| quartz are already accurate enough for most non-enthusiasts.
| Then, after almost being killed by quartz watches in the 80ies,
| the luxury watch industry managed to establish a mechanical
| movement as the desirable item. So there are few expensive
| quartz watches left on the market, which would feature more
| sophisticated movements with higher accuracy. And finally,
| there is a range of higher value watches which receives time
| signals, be it official time signals in several regions or just
| GPS signals.
|
| Cornered like this in the market, unfortunately not much money
| went into high-precisions movements. There are still a few on
| the market from Seiko, Breitling, Omega and Citizen (there
| might be more, but those come to my mind). And of course there
| is the Apple Watch, which is rather affordable and just uses
| NTP to get absolute precise timing.
| serf wrote:
| >yet
|
| I mean, we have accurate electric timepieces now, and the F91-W
| came out in 1989; we had accurate electric timepieces then,
| too.
|
| it's a cost versus value thing.
| teraflop wrote:
| It's easy to make a digital circuit that counts clock cycles
| with perfect accuracy. But for any clock, the actual length of
| each cycle is dependent on analog processes, and it's
| impossible to completely eliminate errors.
|
| 15 seconds per month is about 6 parts per million, which is
| already better than the manufacturing tolerances of a typical
| cheap quartz crystal. There are very few objects of _any_ kind
| that you can obtain cheaply with that kind of accuracy. That
| suggests that, as this article says, Casio is trimming the
| frequency for each watch to compensate for component
| variations.
| faisalhackshah wrote:
| 15 seconds per month is about 6.7ppm. That's well within
| typical crystal oscillator accuracy. If you need more than that
| (without external time correction such as gps or
| radio/internet), you need expensive oscillators with
| temperature compensation or even ovenized units.
| sn_master wrote:
| > all the technological advances that we have
|
| This is 34 years old technology. You can get GPS watches
| relatively cheap and they'd sync with satellites automatically
| and always remain accurate.
| vasqw wrote:
| Yes. I ended up buying a GWM5610 which synchronises through
| radio. It's cool. But still I would have hoped there would be
| a better "local" (i.e. self-reliant) solution.
| mmaunder wrote:
| I'm a big fan of the F105W which is basically the same watch with
| a vastly improved backlight that lights up the whole LCD. It
| makes a great watch extremely usable at night.
|
| I'd also recommend the Casio G-Shock GWM5610 which admittedly is
| about 5 times more expensive at $111 but it has UTC time and is
| absolutely bulletproof, along with radio sync and solar with
| solar charge indicator. It's currently my favorite among my
| modest under $200 collection of watches because it's so
| practical.
|
| I love unconnected watches because they tell the time and have a
| few other basic features without vendors competing for your
| eyeballs in constantly evolving ways.
|
| Side note: I'd avoid Seiko even though they kicked off the quartz
| crisis by launching the world's first quartz watch in 1969, their
| product quality is crappy these days with missing features on
| some nice looking watches, and some bugs in their mechanical
| movements.
|
| On a separate note, I find the luxury watch market to be quite
| hilarious (especially the pretentiously eloquent way a customer
| will describe their "acquisition") but I do keep an eye on it for
| fun and classics like the Rolex Sub Date have dropped by over 20%
| in price on the used market in the past 10 months (source is
| Chrono24 which charts prices). My guess is we'll see the used
| luxury market flooded in 2023/24 as extravagant purchases made
| during boom times are liquidated for cash.
| haunter wrote:
| >radio sync
|
| Such and underrated feature! There is a good list of Multiband
| watches that works across multiple continents that way
|
| https://shockbase.org/function_page_dyn.php?function=multi_b...
| jansan wrote:
| I had been wearing the F105W for about two decades and then
| decided that I want an upgrade. I tried to get as much value
| for my money and ended up buying the LCW-M100TSE-1AER from
| Casio's Lineage collection for 240EUR. Features are
|
| - Titanium casing and strap
|
| - sapphire crystal glass
|
| - Wave ceptor (radio signal receiver)
|
| - Solar cell
|
| - Light (not great, but usable)
|
| If Casio combined these features in a classic looking LCD watch
| that does not cost a fortune, I would not only buy one, but
| three of them. I know, there is the MRG-B5000D-1, but with a
| price tag of 3500EUR, which is more than then times the price
| of my watch with fewer features (no waveceptor) this is a bit
| expensive IMO.
| [deleted]
| TedDoesntTalk wrote:
| > F105W which is basically the same watch with a vastly
| improved backlight
|
| Can't stress this enough. The F-91W is useless at night because
| the backlight brightness is terrible. The F105W has an indiglo-
| style "EL" light that is very effective. The two watches are
| nearly identical from an aesthetic perspective. The functions
| are identical as are the buttons.
| frosted-flakes wrote:
| How does the brighter backlight affect battery life? Doesn't
| the original model have a 7-year battery life?
| galangalalgol wrote:
| I've never had any problems with my f-91w at night. I can't
| use it as a reading light like the EL backlights, but it also
| doesn't ruin my night vision.
| 3pac wrote:
| Indiglo has good looks and function. What I dislike is that
| it requires a high-voltage driver. As tiny and low-current as
| that may be, it is electrically and even slightly
| acoustically noisy, and not something that belongs in a low-
| voltage wristwatch.
| TedDoesntTalk wrote:
| Considering I might turn it on once per night for a second
| or less, I'm not concerned. Is the risk that it affects the
| timekeeping?
| vasqw wrote:
| I love my GWM5610, the only thing I dislike is how hard to
| press the buttons are and the bad display angles. But other
| than that it's a damn brick. And the radio sync is magic.
| jimmyjazz14 wrote:
| I don't really understand your comment about avoiding Seiko
| (and yes as a Seiko collector I'm a bit triggered). In my
| experience Seiko makes absolutely great quality watches still
| with maybe the only issues generally being the occasional
| misaligned chapter ring though I pretty much only collect Seiko
| mechanical watches so maybe the situation is different with
| their quartz watches.
|
| Citizen also makes some particularly interesting quartz watches
| the Chronomaster series (which is a Japanese domestic market
| exclusive) has one of the most reliable watch movements ever
| with a rating of +/-5 seconds a YEAR.
| dougSF70 wrote:
| Seiko 5 automatic movement is on a par with the Rolex
| automatic movement according to my friend who is an official
| Rolex repairer.
| jimmyjazz14 wrote:
| They are often quite similar in design though I'm guessing
| the Rolex uses quite a bit higher quality materials.
| einpoklum wrote:
| F-91W is the watch I wear today.
|
| Actually, my favorite wristwatch - or rather the one I wore for
| 25 years or so - was a W-71. Unfortunately, you can't buy these
| except as vintage second-hand. I still don't understand why that
| is... I always felt it a more "aesthetically-balanced" version of
| the F-91W; plus it had 4 buttons rather than 3, which makes sense
| given the structure both watches. But I lost my W-71 while moving
| out of my last apartment, so... now I've had to settle on the
| F-91W. Ah well.
| [deleted]
| Ecco wrote:
| Dumb question: is it legal to share a die shot like this one?
| What does copyright law say about this?
|
| I mean, yes, the author took the photo himself but what about the
| underlying material? Can I share a photo of an entire book? Do I
| own the copyright to a photo of a painting?
| schemester wrote:
| If the layout had copyright protection, this would still be
| fair use.
| petodo wrote:
| why not? you are free to disassemble your computer and take
| photo of motherboard or whatever hardware you have, I don't see
| how is taking photo of die different
|
| you can have copyright to your own photo, but not to pictured
| design
| Ecco wrote:
| Well a die design, just like code, is definitely some form of
| intellectual property and covered by copyright law. So I
| think a more fair comparison would be a photo of an entire
| book.
| squarefoot wrote:
| The die design tells what parts are there, not their values
| or characteristics; cloning a chip just by looking at the
| die would require a lot more research.
| rwmj wrote:
| It might be a problem if the photo was reverse engineered
| into a schematic, which would also imply much more detail,
| but in this case it's just a photo of something cool.
| ekianjo wrote:
| > Well a die design, just like code, is definitely some
| form of intellectual property and covered by copyright law.
|
| you can consume a book just by looking at it. You can't
| "read" a die-shot as easily.
| addaon wrote:
| > is definitely some form of intellectual property and
| covered by copyright law
|
| I'm not sure if you meant to suggest that "some form of
| intellectual property" implies "covered by copyright law",
| but this is untrue in general, and untrue in this specific
| case.
|
| Copyright does not cover mask works; see [1] for
| discussion, from which quote: "Copyright law ONLY protects
| an original work of authorship IF the work is non-
| functional. But the etching designs on computer chips ARE
| functional."
|
| [1] https://revisionlegal.com/copyright/mask-
| works-101-copyright...
| jonatron wrote:
| "Can I share a photo of an entire book?"
|
| No is the short answer to that one.
| MonkeyClub wrote:
| Actually you can share a photo of an entire book - it's only
| that you can't share photos of all its individual pages as
| well...
|
| (Sorry, tried hard to resist, and failed.)
| bmurray7jhu wrote:
| In the US, semiconductor mask layouts are not eligible for
| copyright. Instead, the mask layout is protected under the
| Semiconductor Chip Protection Act of 1984. The Act grants
| rights similar to traditional copyright, but with a shorter
| period of protection and a more permissive framework for
| derivative works.
| Ekaros wrote:
| I don't think it is any different than taking a photo of your
| car engine or gearbox or any such component.
|
| Issues comes when you start to make copies.
| nickdothutton wrote:
| Casio is an under leveraged brand. One of the few that could, I
| think, be taken into more product areas than it is currently.
| There's brand equity there they are not fully leveraging.
| MonkeyClub wrote:
| Is that a Swiss flag on the lower-left corner, or some kind of
| pads?
| qwezxcrty wrote:
| Maybe an alignment marker for layer stacking.
| sweetjuly wrote:
| Yup! These sorts of crosses are used to align
| photolithography masks. Here's a similar example: https://www
| .seas.upenn.edu/~nanosop/images/alignmentmarks2.p...
|
| There are a lot of other structures used to characterize the
| alignment and other fancy structures which support machine
| alignment for newer (than like the 90s) processes.
| faefox wrote:
| Maybe a fiducial marker?
| MayeulC wrote:
| Possibly a (coarse, as it's the topmost) mask alignment target.
| aliljet wrote:
| This is a remarkably interesting image. How do these guys even
| get these shots? I'd love to do this on all kinds of things at
| home..
| sweetjuly wrote:
| I really like this one Defcon talk on chip decapping [1]. It's
| a pretty nasty process but absolutely one you can do on your
| driveway (poor man's fume hood, don't tell the EPA) at home.
| You can then just use a standard front lit microscope to take
| die shots.
|
| [1] https://youtu.be/0Z4aF-qiziM
| kens wrote:
| For die photos, you want a metallurgical microscope, one that
| shines light down through the lens. A typical microscope shines
| the light from underneath, which works well for biological
| samples, but not so well for chips.
|
| The tricky part is decapping the chip. The easy way is to get a
| ceramic package, which you can decap with a chisel. Or a metal
| can, which you can open with a hacksaw. With a standard epoxy
| package, you can heat it with a hot air gun and twist it, and
| you have maybe 50% chance of the die separating from a package.
| The best way for epoxy packages is boiling sulfuric and/or
| nitric acid, which has obvious issues.
|
| The other aspect is that you need to stitch together a bunch of
| images to get a high-resolution photo. I use Hugin, which lets
| just say that it has a learning curve.
| [deleted]
| diydsp wrote:
| Seems like two large similar rectangular logic areas.... maybe
| one is state machine and one is display?
|
| Or maybe one is clock/date and one is UI?
| kens wrote:
| I think it's one blob of standard-cell logic on the left with
| power routing through the middle. I don't think there is any
| visible partitioning into functionality in this logic. The
| large amount of analog circuitry in the right half is a bit of
| a puzzle. It looks like some large capacitors, maybe a charge
| pump for something?
| addaon wrote:
| This is outside my wheelhouse, but I assumed that the large
| capacitor area was a (trimmable) capacitor bank that could be
| put in parallel with the load capacitor on the (external)
| quartz oscillator, allowing calibration to counter some unit-
| to-unit variant in crystal frequency.
| kens wrote:
| That's a possibility, but I don't see any laser-trimming
| marks on the big capacitor. Another option would be
| selecting capacitors with fuses, but I don't see any fuses
| or capacitors with powers-of-two sizing. With the
| complexity of the circuitry in the right hand side, I think
| there are a bunch of analog things going on.
| makomk wrote:
| The calibration for quartz crystal variance in these
| watches is done much, much later in the manufacturing
| process using solder bridges on the PCB - people have
| reverse engineered it. I think there are watch oscillator
| chips out there with one-time programmable calibration
| (particularly for analog watches) though.
| _HMCB_ wrote:
| Looks like a city from overhead. Amazing.
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