EEVblog #389 - Casio Calculator Investigation

[EEVblog]

Dave.

[mickpah]

want to see weird Calculator internals ?
MY HP 32E's man IC is not soldered at all ( still works 30 years later too! god am I that old ?)
http://www.keesvandersanden.nl/calculators/hp32e_repair_2.php

[EEVblog]

Inside my old HP42S
No, I did not crack open that chip, that's how it is!


Dave.

[IanB]

Hmm. We often think about having many layers on a complicated PCB. But how many layers on a chip? It must be just as complicated as a PCB inside there with all those terminals around the edge.

[Zad]

Chris Gammell is the bloke to ask about number of layers in a chip. You might be surprised how few actual metallisation layers they have.



My fx-3600p in this photo draws a huge 68 uA! Vintage 1982 ish. But still on the original battery!

[EEVblog]

Hmm. We often think about having many layers on a complicated PCB. But how many layers on a chip? It must be just as complicated as a PCB inside there with all those terminals around the edge.

As always, "it depends".
These calcs are not complicated and often contain very basic 4 bit CPU's.
Just like a PCB's, you'd be surprised at the routing density you can get with just two layers.

Dave.

[pickle9000]

How many other words can be made on a calculator?

[jeroen74]

That last calculator is not a Casio, it says Sanyo on the flex pcb (at 13:19).

[EEVblog]

That last calculator is not a Casio, it says Sanyo on the flex pcb (at 13:19).

That's the solar cell. It's a Casio.

Dave.

[tom66]

I note that Casio seems like like Sanyo solar cells.

I had an FX 83-GTes with a dodgy battery contact causing the battery voltage to drop out.  Cause eventually was resolved by cleaning the terminals. The display would get really dim and the calculator -would- slow down calculation. If it dropped even further it would corrupt the display RAM with random data and usually the calculator would need a reset.

[robbag]

Dave you are a kid at heart. I remember the days during school where you would write words on the calculator........BOOBIES
Clever.

[AlfBaz]

Quagmire from family guy likes calculators to

Calculator Boobs

[jeroen74]

together with a friend I once made a list of words you could make, we ended up with over 110 words or so.

[Stephen Hill]

A quick Google found this list of 250 words:

http://paperlined.org/apps/wikipedia/offsite_content/Calculator_spelling.txt

[Ketturi]

It would be interesting to see follow-up video about comparing those old photocells to cutting edge technology, and to normal new calculators to see how much solar power technology have developed. I think that power consumption have gone down, and not the photocells, but we have also battery charger etc. using solar cells so I'm not 100% how they work, does they have higher cell voltage and efficient switch mode converter to produce higher charging current or what?

I had similar calculator as the last calc shown in video, brilliant device. I also took it apart when I got it, very interesting construction. It's photocell couldn't power it in classroom and without battery it were useless. Then I bought TI-92 which I'm using still at this moment, sucks battery 8mA when idling and 40mA doing some processor intensive calculation! Always crying backup batteries in my schoolbag

[Matje]

The weird mounting of this chip is probably just a variant of "flip chip" mounting. It seems this technique is quite old, Wikipedia says IBM did it in the 60ies. The yellowish gunk with the bubbles in it is probably the "underfill" needed.

In a way flip chip is like BGA, just with the expensive chip packaging left out.

[marcel.o]

I saw the vid and didn't know it could be that interesting!!


But look what I found in my drawer..




And it still works!!

1 Chip (week 49 1976!!)
1 dc-dc converter for de vfd
1 valve like 9 digit vfd

would be fun to measure at some points.. (some slightly high voltages for the tube enz.)

[jancumps]

A quick Google found this list of 250 words:

http://paperlined.org/apps/wikipedia/offsite_content/Calculator_spelling.txt

They forgot a few dutch words like
BLOESLOS
LESBIS
and the calculation LOL + LOL = HIHI

[LaurenceW]

Dave, surely that is an early form of BUBBLE MEMORY? 

I'll get my coat

[EEVblog]

Dave, surely that is an early form of BUBBLE MEMORY? 

That one, Sir, I will pay! 
Wish I'd thought of it at the time 

Dave.

[G7PSK]

Very interesting video again, Made me look out my Casio that I bought in 1975 or 1975 and take it apart, it still works the only thing that is that the leatherette pouch has disintegrated long ago but the cardboard box and instruction sheet survive I tried to find the invoice but to no avail, I know that I purchased it from Heffers book shop stationary department in Cambridge 1974 or 1975.   

[And!]

Maybe it would be interesting to put current variation on oscilloscope,
and find out how calculation is affect on current consumption variation ?
(Power-Analysis Attack  )

[tom66]

Casio fx-83GT+

VPAM one -- waiting for the hate mail!

[marcel.o]

Very interesting video again, Made me look out my Casio that I bought in 1975 or 1975 and take it apart, it still works the only thing that is that the leatherette pouch has disintegrated long ago but the cardboard box and instruction sheet survive I tried to find the invoice but to no avail, I know that I purchased it from Heffers book shop stationary department in Cambridge 1974 or 1974.

[tom66]

Interesting -- Was playing around with my calculator.

Shift+7+ON activates diag mode. Press 9 to go through display test. Press Shift five times to get to version screen and note "Pd-" as the option.

Pencil in using a graphite pencil one of the Pd1..7 options, and activate the same version screen... and see "PdN" where N is the one you penciled, or a "?" if you pencile more than one.

However... despite doing this, I don't notice any difference. I think I need to reset the calculator to enable the extra options. The "Internet" reports that P4 on older Casios makes a low-end one behave like the 991ES with the differentiation/integration/solve features.

[FJV]

Some form of alternative pcb may be in the future for use with 3d printers.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049365

Should be fun, I guess.

[mikeselectricstuff]

I like this Olympia space-age looking thing :


Magnets & reed switches for the keys, plug-in PCBs.

[free_electron]

Number of layers in a chip is hard to determine. There are a bunch of sacrifical layers that are created , removed , created again , removed again.
In terms of metallic interconnect the earliest chips had only 1 layer. modern chips have up to 6 layer metal the top 2 of which can be copper if needed but mostly are aluminum.
Then there is all the intermediate layers : nitride layers , polysilicon layers , the implanted structures.
Some masksets contain up to 100 masks each of which creates a 'layer' in the chip. Not all those layers remain behind. some are stripped as they serve as a temporary shield for a process step. Other layers are combined into 1 . they contain multiple structures that are made a different way but in the crosssection occupy only '1 layer' but they are made independently.

Masksets are horrendously expensive. They are essentially a quartz plate with a chrome film vacuum deposited onto it. this is then coated with a photoresist and exposed using an electron beam. after development the mask is plasma etched to removed the exposed chrome. the structures on the plate are much larger than they need to be on the chip.
the mask is covered with a reticle ( a thin film of celluloid offset about 1cm ) if any speck of dust were to fall on the reticle the distance is far enough we can focus straight through this. A 'stepper' uses a deep UV lightsource ( typically a quartz sphere containing some noble gases , which are excited using an X-ray source ) to send the light through the mask and the optical array. the wafer is then 'stepped' with this image. the mask holds, depending on size, the patterns for 1 to 20 chips.

[IanB]

Number of layers in a chip is hard to determine. There are a bunch of sacrifical layers that are created , removed , created again , removed again.
In terms of metallic interconnect the earliest chips had only 1 layer. modern chips have up to 6 layer metal the top 2 of which can be copper if needed but mostly are aluminum.

Thanks for the answer. I was basically interested in the interconnect layers, where one conductor has to "cross over" another without making contact like the traces on a multi-layer PCB. It sounds like the answer is up to about 6.

[alm]

But probably less than six in an eighties-vintage IC.

[free_electron]

Eighties vintage. One or two maximum. Three metal was end nineties...

[jeroen74]

I guess that also depends on the complexity of the chip. A calculator chip isn't particularly high tech or demanding. And just as with PCBs, component placement is a very big factor in how easily a PCB can be routed. From what I read, the complexity in FPGA/chip tools is in the placement algorithms, not the routing.

[tom66]

The Casio VPAM ones clearly use a micro of some kind, the diag mode mentions "ROM" and "Read OK". But I wonder about the more basic ones. Do they use ASICs or some 8/4-bit micro core?

[jeroen74]

I've been wondering this myself for ages too I guess the basic ones just have a simple ASIC with a 4 bit core that's highly optimized for calculator operations. Certainly nothing general like a PIC or AVR, maybe something highly obscure like from NEC.

For fun, a while ago I designed my own four bit core to make a simple four function calculator and wrote the code for it. An interesting trade off is whether to include a special instruction to get something done or use multiple, more simple instructions but use more ROM. I don't know what's cheaper in silicon, logic or ROM.

Currently it's only running on a simulator on a PC, but I still plan to create an actual hardware version, with an AVR emulating this P-Code (actually, the first calculator using the 4004 used P-Code ), the challenge to keep everything within 2K of Flash.

edit:
One even more totally outrageous thing I did a couple of years ago, was reimplementing the original HP-35 with a FPGA, from the descriptions and code from the original patents which are very detailed. Unfortunately, I never got round to actually finishing it 

[PaulS]

Very weird watching this, I have the exact same calculator (fx-260 solar) sitting on my desk. I can tell how bright your lab is, when I do 69! the screen blanks for a few seconds, then it displays the result.