Casio fx-5000F Scientific Calculators: parallel computing made simple

[jebem]

Not the conventional parallel computing, that is.
But one can use them in parallel to speed up some tasks.




With 128 stored formulas ready to be used, this model was very popular among students and professionals at the time, and it is probably one of the best pocket Casio calculators from the late 80's.

One of my beauties was made in 1991 according to some internal component date codes.








Forensic test result: 9.0000156854
Full contrast on to show all the LCD pixels and annunciators.

[jebem]

Tear down

to inspect the inside and have a cleaning.
2 x CR2032 batteries for a total of 6Volt are required to power this unit.




Inner frame in place over the PCA.
Six self tap screws fix it in place.
Note the shielding/grounding spring at top center. Care is required to inset it in inner frame pass thru hole, while keeping the power switch in the correct position.
Power switch in its bed at the inner frame.




Inner frame latches, at the display side.





PCA installed over the keyboard membrane.
Note the shielding/grounding spring at the top center.
The PCA is free now to be lifted. Care is required to not damage the LCD display when removing it from its position.



Keyboard membrane and keyboard rubber keys side view.




Keyboard membrane over the rubber keyboard, PCA side view.
Rubber keyboard painted keys.

[jebem]

Internal components detail.

Integrated Circuits:

- Hitachi HD62001A04 1G 33 processor (1991)
- OKI M5268V-H1 1716 controller
- Hitachi HD61914C 1G 43 1KByte SRAM (1991)

The HD62001 processor is used in several Casio and OEM calculators only changing the firmware, for example:
- Casio fx-3900P: HD62001A01 6L 13
- Radio Shack EC-4023: HD62001A04 (OEM of fx-5000F)




The Printed Circuit Assembly keyboard side, after removing the keyboard key's foil.




General parts view.

[Alejandro Paz(Germany)]

It would be interesting to know what kind of processor they use.
Btw, I enjoy your tear-downs and comments a lot !

[jebem]

Good question on the processor type, Alejandro.

The only source of information on these Casio internal architecture that I'm aware of is from Piotr Piatek.

Apparently these Hitachi or NEC processors from that period are custom designed for the job and are not based on any other common model like the Zilog Z80 or the Intel 4004 or 8080, or the 6502 series.

Crossing that information from Piotr Piatek with some more pictures of Casio internals from other folks like Kyoro and checking the SRAM memory types and interfaces, it seems that there are two main groups of processors concerning the data bus size that may imply a specific ALU size as well.

- 4-bit data bus processors:
HD61747 fx-5500, fx-5200P, fx-4000P, FC-200, PB-120, PB-500,
HD61913 fx-700P
HD61917 PB-700

HD43191 fx-602P, fx-702
HD43108 fx-502P


- 8-bit data bus processors:
HD61700 8-bit PB-1000

HD62002 8-bit fx-603P
HD62076 8-bit SF-9300
HD62021 ?-bit fx-61F (edited to add a link to my thread on it)
HD62001 ?-bit fx-5000F, fx-3900P

There is a pattern in the naming convention, where the HD61 series are 4-bit (with one exception only for the HD61700) and the HP62 are 8-bit processors.
So this HD62001 Processor is very close to the HD62002 and therefore could be a 8-bit processor.

Additionally, why did Casio use a interface controller between the processor and the SRAM memory on this fx-5000F?
The only cases I'm aware of are to allow a 4-bit processor to access a 8-bit data wide SRAM, or the other way around like in this case, where a 8-bit processor access an HD61914C 4-bit data wide SRAM memory.
(The HD61914C is very well documented and uses a 4-bit data wide bus).

So, probably this Hitachi HD62001 processor uses a 8-bit data bus connected to a HD61914C 1024 4-bit words SRAM thru a OKI M5268V-H1 interface controller that is aggregating SRAM 4-bit data word pairs into 8-bit words to present to the CPU.

I can't find information on the OKI M5268V-H1 either, but looking into the circuit I can see this OKI chip interfacing the SRAM to the Processor.

[SeanRiddle]

(02-26-2017 11:12 PM)jebem Wrote:  I can't find information on the OKI M5268V-H1 either, but looking into the circuit I can see this OKI chip interfacing the SRAM to the Processor.

I came across your post while searching for info on the OKI M5268. That chip is actually a ROM that uses the same interface as the HD61914 SRAM (and Panasonic MN6404 ROM). I assume the calculator requires more ROM space than the HD62001 has internally, so they had to add an external ROM. If I can find an inexpensive Casio fx-5000F on ebay, I'll see if I can dump the ROM.

[Eddie W. Shore]

What would be an example of parallel computing whit the fx-5000F?

I think the current fx-5800P has tons of built in formals, would that machine be capable of parallel computing?

Thanks.

[freelanzr]

(10-06-2019 12:25 AM)Eddie W. Shore Wrote:  What would be an example of parallel computing whit the fx-5000F?

I think the current fx-5800P has tons of built in formals, would that machine be capable of parallel computing?

Thanks.

Not unless you had two of them;-OP has 4? - so parallel programming squared is obtainable.

I want one.
Actually... now I want two.

[jebem]

(10-03-2019 03:47 AM)SeanRiddle Wrote:  

(02-26-2017 11:12 PM)jebem Wrote:  I can't find information on the OKI M5268V-H1 either, but looking into the circuit I can see this OKI chip interfacing the SRAM to the Processor.

I came across your post while searching for info on the OKI M5268. That chip is actually a ROM that uses the same interface as the HD61914 SRAM (and Panasonic MN6404 ROM). I assume the calculator requires more ROM space than the HD62001 has internally, so they had to add an external ROM. If I can find an inexpensive Casio fx-5000F on ebay, I'll see if I can dump the ROM.

If it is a rom, and it makes sense now, then the processor seems to be a 4 bit and not 8 bit as I especulated initially.

[jebem]

(10-06-2019 12:25 AM)Eddie W. Shore Wrote:  What would be an example of parallel computing whit the fx-5000F?

I think the current fx-5800P has tons of built in formals, would that machine be capable of parallel computing?

Thanks.

I was just making a joke to show of my then four machines (I have more of this model now, some defective or else having the rubber key labels faded away badly).

[SeanRiddle]

(10-07-2019 10:45 PM)jebem Wrote:  

(10-03-2019 03:47 AM)SeanRiddle Wrote:  I came across your post while searching for info on the OKI M5268. That chip is actually a ROM that uses the same interface as the HD61914 SRAM (and Panasonic MN6404 ROM). I assume the calculator requires more ROM space than the HD62001 has internally, so they had to add an external ROM. If I can find an inexpensive Casio fx-5000F on ebay, I'll see if I can dump the ROM.

If it is a rom, and it makes sense now, then the processor seems to be a 4 bit and not 8 bit as I especulated initially.

I bought a Radio Shack EC-4023, which is an OEM of the fx-5000F. I was able to dump the ROM from the M5268, and I decapped all the calculator chips and took pictures: http://www.seanriddle.com/m5268.html

[Eddie W. Shore]

(10-07-2019 10:49 PM)jebem Wrote:  

(10-06-2019 12:25 AM)Eddie W. Shore Wrote:  What would be an example of parallel computing whit the fx-5000F?

I think the current fx-5800P has tons of built in formals, would that machine be capable of parallel computing?

Thanks.

I was just making a joke to show of my then four machines (I have more of this model now, some defective or else having the rubber key labels faded away badly).

LOL You had me going.

[Dan C]

I just got a fx-5000F for cheap, and in a mint condition too!
Seems to be a very nice machine, reminds me of my fx-4000P in design and looks.

[luke7110]

Hi, I also bought this calculator, this was my first serious calculator when I was kid ?
Good cosmetic condition but sold as non working for cheap.
The only electrolytic capacitor leaked a bit, I swapped it and had to repair a corroded track in the area. It now turns on and at first I though I repaired it, cause I can type and screen looks ok, but I just can't calculate. If I try a "1+1 EXE" screen goes blank with just a - in the lower right corner.
Same if I try to call a formula ex "1 FMLA".
I reflowed and cleaned all the joints, but it didn't improve the situation.
I guess main CPU is OK and the problem is coming from RAM ?
After reading all the posts and understanding that a ROM is in-between CPU and RAM, (+ formulas are stored inside the ROM), could it be the ROM instead of RAM?
Still, I guess RAM are more prone to fail.

Any thoughts ?

[Dave Britten]

(09-30-2022 08:41 AM)luke7110 Wrote:  Hi, I also bought this calculator, this was my first serious calculator when I was kid ?
Good cosmetic condition but sold as non working for cheap.
The only electrolytic capacitor leaked a bit, I swapped it and had to repair a corroded track in the area. It now turns on and at first I though I repaired it, cause I can type and screen looks ok, but I just can't calculate. If I try a "1+1 EXE" screen goes blank with just a - in the lower right corner.
Same if I try to call a formula ex "1 FMLA".
I reflowed and cleaned all the joints, but it didn't improve the situation.
I guess main CPU is OK and the problem is coming from RAM ?
After reading all the posts and understanding that a ROM is in-between CPU and RAM, (+ formulas are stored inside the ROM), could it be the ROM instead of RAM?
Still, I guess RAM are more prone to fail.

Any thoughts ?

Have you pressed the Reset button on the back with the calculator turned on? Older Casios usually don't have automatic initialization of memory, and can act a bit goofy if you don't reset them after installing batteries.

[luke7110]

Hey Dave, thanks for the tip! It just worked !!
I feel stupid now, at least I don't have to mess with smd RAM chips
I'm super happy!!

[Dave Britten]

(10-04-2022 07:31 PM)luke7110 Wrote:  Hey Dave, thanks for the tip! It just worked !!
I feel stupid now, at least I don't have to mess with smd RAM chips
I'm super happy!!

Great! I'm glad that worked. I don't think I've seen that specific failure symptom, but I've seen enough weird behaviors due to uninitialized memory that I always try the reset button first.