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Casio-F-91W die-shot

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Re: Casio-F-91W die-shot

#21

Post by addaon »

Ecco wrote: post #4
petodo wrote: post #3

Earlier quoted context omitted.

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

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.

> 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...

Re: Casio-F-91W die-shot

#22

Post by sn_master »

vasqw wrote: post #12

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?

> 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.

Re: Casio-F-91W die-shot

#23

Post by addaon »

kens wrote: post #10
diydsp wrote: post #9

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?

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?

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.

Re: Casio-F-91W die-shot

#24

Post by mmaunder »

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.

Re: Casio-F-91W die-shot

#25

Post by Tor3 »

vasqw wrote: post #12

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?

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).

Re: Casio-F-91W die-shot

#26

Post by haunter »

mmaunder wrote: post #24

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…

>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...

Re: Casio-F-91W die-shot

#27

Post by TedDoesntTalk »

mmaunder wrote: post #24

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…

> 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.

Re: Casio-F-91W die-shot

#30

Post by 3pac »

TedDoesntTalk wrote: post #27
mmaunder wrote: post #24

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…

> 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.

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.
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