I went to the page expecting to rant about how it's not actually credit card size because of the thickness and was for once pleasantly surprised! Kudos to the author! It looks great!

I was thinking all that too and considering commenting about being sick of those credit card size claims, but after seeing the footage I am genuinely impressed. Great work there.

This post - the title made me remember ... ( as a credit card is about the same size as a business card )

A Linux Business Card CD is a miniature, credit-card-sized optical disc containing a stripped-down, bootable Linux operating system. They hold around 50MB to 100MB of data and were highly popular in the early-to-mid 2000s

More info at https://en.wikipedia.org/wiki/Bootable_business_card

yeah, also reminded me of wifi sd-cards: https://hackaday.com/2016/06/30/transcend-wifi-sd-card-is-a-...

Seth Schoen (<https://news.ycombinator.com/user?id=schoen> at HN) was lead dev in building one of the best-known instances of these, the Linuxcare Bootable Business Card (LNX-BBC), and has occasionally commented on that here:

<https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...>

Or the Rex 6000 or other PCMCIA cards:

https://en.wikipedia.org/wiki/REX_6000

I had one of those - I think it is still in my office desk.

this is really cool. I didn't know we had these

These things were cool! I believe I had some drivers installed via some of them, and a Kubuntu livecd.

What fun!

I’d love to also go the opposite direction, a full-sized laptop with an ESP32 running tiny386 and Windows 95 ^_^

https://www.hackster.io/news/he-chunhui-s-tiny386-turns-the-...

This could be great if the rest of the chassis was filled with batteries.

Developer here :)

Just saw this and love how I got the 100th or so "Does it run DOOM?". Even now officially an issue on GitHub. Does that mean I now have to deliver?

> Does that mean I now have to deliver? Well, if you'd like to, you're free to do so! If not, somebody else could do it. You're not your audience's slave

I know it was intended as a joke but still..

How optimal is the PCB density? Do you think there is significant room for improvement to have a smaller PCB and larger screen and/or battery?

So... it's not DOOM-complete?

Teenage Alan T. would be so disappointed... :D

> A fully working computer that is literally the size of a credit card.

Nit: A (chip) credit card is already a fully working computer :)

Only if it is inside a specially designed radio field and with no independent IO. Feels like a battery and IO justify the 'fully working' differentiation.

Interesting philosophical question: Is a tower PC that's not plugged into anything (neither power nor a keyboard or monitor) a computer? Does computation happen if nobody can perceive it? And is a computer a computer even between two CPU cycles?

> no independent IO

I would challenge that! How is a smartcard different from a server in a qualitative sense? Both get all their I/O over the network.

Some cards even have a display, fingerprint reader, or can blink an LED (the latter unfortunately only indiscriminately when powered up, not in response to any computation, I'm afraid).

Is a bare SoC a computer? You can poke the pins to provide power and I/O.

The interesting thing about this project is that this computer can function independently within a credit card sized space.

I've never heard a definition of a computer to include its power source.

IO is of course required.

Last week (87 points, 7 comments) https://news.ycombinator.com/item?id=48251528

Thanks! This project is cool enough that I think we can tolerate another thread about it, especially since that post didn't get too much frontpage time. I'll put a link to it at the top though.

Thanks! Arbitrary application of rules is nothing short of what I would expect from CCP LOVER DANG.

Very cool! Love it...

But...

The battery is likely to be squeezed quite a bit after this is put in my wallet, and in my pocket.

Lithium batteries do not like to be squeezed. They tend to signal their distress with some type of heat, usually accompanied with a small fire and probable smoke as well.

A distressed battery is very insistent upon everyone to see it's state of mind...

This is discussed in the post.

Hidden in here is the coolest part, that the author made flex PCBs at home

Just in time for DEFCON. We built many of these types of badges

I love these kind of projects. M5Stack Cardputer Zero launched on Kickstarter last week and already hit their goal

https://www.kickstarter.com/projects/m5stack/cardputerzero

Prologium is depositing thin film solid state batteries onto flexible ceramic insulators. They have some demos of single cells that appear to be thinner than 1mm continuing to operate after bending in half.

https://prologium.com/tech/core-technology/

Coincidentally, the xteink x4 has the same CPU, an e-paper screen and is close to credit card sized.

If you think 1.33x1.28x7.76 times bigger is close to the same size. I don’t.

I would love if the screen could take up more space, even at the expense of a little extra thickness.

That actually exists, with even the same CPU but no NFC: https://www.xteink.com/products/xteink-x4

I think that there could be a wider screen if such formats are available. Once we have betavoltaic batteries, the entire card can be screen.

I'm not sure beta voltaics will ever reach LiPo densities. All materials I know would be unwise to place in your wallet, or anywhere near your body.

If we are OK with a battery and a beta voltaic source, a tritium one is reasonably safe and can trickle charge the battery when the device is in deep low power mode. The battery can still be charged by the induction coil.

love this. would be cool if we can see and perform all kinds of banking txns on this. Think ledger but all in one card. Super cool. Even cooler would be card to card money transfer without use of swipe machines

If "ledger on card" interests you, then you might enjoy Japan's FeliCa cards. They store balance locally on the card so you can pay very quickly, no network required.

Do these cards solve the electronic cash problem (in a completely different way than cryptocurrencies)? What I mean is that

- Are the card readers special/trusted issued by bank/govt in some way? Or you can transfer money from one card to another yourself fully offline?

- Is there any requirements that the transfers have to be eventually communicated to the bank by one of the parties to be fully resolved?

- Has someone managed to create fake cards with fake money in it, or this is impossible by design?

How do you recharge it? Do you have to swap the battery?

Hey, developer here :)

I used an ultra thin LiPo, so you can actually charge it. USB is obviously not an option but it uses magnetic pogo pins on the back side ^^

It seems like it might be a little expensive for a business card...

Let's see Paul Allen's card.

Or, it would be interesting to see how this would fare in American Psycho.

Can it run DOOM?

I've got the question like 100 times easily, and I love it.

And yes, if you accept ~0.7FPS

You mean, 1.5 SPF :-D :-D

Try NGK EnerCera for battery.

This is great, and I love it, and I hate to be saying this, but it's not literally the size of a credit card, it's 0.2mm thicker.

Fair enough, but I acknowledged that and it's 0.24mm thicker if we want to be exact. Here's a quote from my Git Repo:

"Official ISO7816 smartcards are specified at 0.76mm thickness, but many real-world cards slightly exceed this in practice. The target for this project was simple: Stay around ~1mm total thickness and preserve the illusion of a normal card."

Hey, works for me, I just got OCD from the title's usage of the word "literally".

Run Unix v6 on it :) 16 bit and works with like 80kb of ram

Fuzix might be another option: <https://fuzix.org/>.

Works on the RISC-V 32-bit processor, sometimes.

__This__ is where all those trusted app parts should go - a smart card with e-ink display that can provide high security assurance level and where I won't mind that it's locked down because it has only one purpose.

__Not__ to my smartphone, effectively preventing me from modifying the system in the name of security. A banking app can use a card like this and on the display I could for example see where a transaction would go and then I could accept it, possibly even with a biometric identification.

This would enable me to keep my smartphone customizable and banking apps secure at the same time.

[apologies for the rant]

And it would communicate using?

Do yourself it!

dyi = Do Yourself It?

I want this, but only for one thing: email.

I already use an pwnagotchi, and it works great for this - but its a bit bulky.

If I can get this set up and working, it'll be my main interface to email.

legendary

It’s got more horsepower than my first desktop computer

In what way is it not a computer?

Right, it doesn't compute. Apologies for the lie.

Your definition of "computer" is incorrect.

First thought: cool! Second thought: e-waste

(same reaction as single-serve coffee pods, circa 2023)

Good point. Ideally it would be the opposite of waste if it can save you from several cards. But banks would never certify such a multi-card system unless a big company pushes it forward.

Otherwise I'm sure people might use this to hack some terminals :P