Core Memory Upgrade for Arduino | Hacker News Reader

Core Memory Upgrade for Arduino

hackaday.com

75 pointsingve13 comments

Core eventually miniaturised into https://en.wikipedia.org/wiki/Ferroelectric_RAM , which remains in limited use (TI has a series of MCUs with FRAM instead of EEPROM) --- and one curious application is in the toner cartridge DRM chip of a Lexmark laser printer, for which there is this ongoing reverse-engineering effort:

https://www.eevblog.com/forum/projects/lexmark-toner-chip-ti...

(Normally those use EEPROMs, so the choice of FRAM is a bit odd.)

You make it sound as tho FRAM is old technology... its actually just starting to be used in volume (in microcontroller based systems). FRAM has some very desirable properties compared to current technology uC that use both SRAM & FLASH. Its still slightly expensive at this point in time but that will solve itself in time.

> FRAM has some very desirable properties compared to current technology uC that use both SRAM & FLASH.

Could you please elaborate?

it's as fast as sram but persists like flash

> Core eventually miniaturised

Well, sorta. The physics behind the device is the same, but the manufacturing is distinct. Core was produced by threading tiny ferroelectric donuts cut from an extruded tube onto copper wires. There's no "miniturization" continuum between that and FRAM, which is produced with planar lithography.

It's a very cool but strangely marginal technology; it's not going to have the density of Flash any time soon, sadly.

The interesting property of FRAM is that it behaves in same way as core. Random access and non-volatile (and without significant write/erase wear). End result is that for applications that will fit into practically sized FRAM array you essentially do not have to thing about restoring the state after power loss, because the state simply is there as it was on core-based minicomputers (one thing that I find funny is that MSP430FRxxx in fact is PDP-11 on single chip with slightly different instruction encoding).

There seems to be some confusion in this thread between ferroelectric vs ferromagnetic.

These are two distinct physical phenomena. FRAM is based on the former whereas magnetic core memory is based on the latter.

With this in mind, I’m not sure it is really accurate to regard FRAM as a successor to magnetic core memory.

If you want to spend a while learning more about how magnetic cores work check out these videos made by the US Army in the 60s:

https://m.youtube.com/watch?v=HPT7Wtp3yoo https://m.youtube.com/watch?v=An-GIhx0z4c

I wonder if there is anything unique about this that might make it interesting to use in a sampler or a synthesizer or something .. maybe some random noises that could be generated by stroking the core, or some such things ..

I doubt that storing digital representations of sounds on the cores and then stroking the cores would result in any modification of the data. You could run a wire with current next to the cores to induce bit flips, but what happens to the sound would depend on the format of the data stored on them.

You could put an inductor in or around the array, which could pick up magnetic impulses from currents used to program the cores. If you amplify the voltage coming out of the inductor and sample that, it could result in interesting random sounds.

You could play with the distortion induced by core saturation, perhaps. Go full analog and run the audio directly through the core array.

> Of course, the Arduino can’t directly run programs out of the memory...

Use the Atmel ATmega2650's external memory bus on the mega and you could. Or at the very least, a few variables.

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