Tech-nerd question about flash memory

[MarcusGHedwig]

Ok, so I understand that flash memory is considered volatile because it will be erased if there's not a minimal electric charge, unlike a magnetized disc - so I assume that means that all flash drives have a small button-cell battery, and thus if one were to leave one unused for awhile, and the charge dissipated, the data would be lost? And for that matter, assuming the battery is rechargeable, when it gets to the point where it won't hold a charge, that once again would cause one to lose ones data, correct? (or if it's not rechargeable, then it'd just die)

Finally, how do SIM cards store information, when there's clearly no room for a battery in them?

Thanks in advance for the enlightenment

 

[slashvanyoung]

Flash memory doesn't use one central battery. Here is a schematic of one flash memory cell to visualize things:

The Floating Gate acts much like a capacitor, holding the charge. With every writing access to a flash card, these Floating Gates get recharged and will hold your memory for several years without a charge. SSD manufacturers usually state about ten years.

A SIM card works differently. It's a combination of I/O, CPU and memory:

The I/O layer acts as an interface between the card's CPU and the phone. The card's CPU itself is mainly for memory management but also able to execute small programs. The ROM stores the OS of the SIM card, as well as things like company brandings. The RAM will temporary store the information that is in use at the time and the EEPROM will hold your personal data like contacts. EEPROM works kinda similar like Flash concerning the main principles.

That EEPROM is like flash memory considered to be non-volatile.

 

[Skinny Viking]

My EYES!!!

 

[slashvanyoung]

It's just a dumbed down version of the very basic concepts.

 

[TheWinterSnow]

Marcus, Flash Memory is non-volatile, because it does not need an external source of power to store information. While the charges of a cell will dissipate over time the, it is still years before the charge will drop enough where the information would be non readable and essentially lost. A flash cell is just a modified MOSFET, as they add the floating gate which acts as a capacitor, and as you know capacitors hold charges for a long time (kind of like how tube amps can hold "lethal" charges even years of being unplugged and unused).

as slash also pointed Sim cards are basically microprocessors that store information on the "Electronically Erasable Programmable Read Only Memory" Or EEPROM which for the scope of this conversation is the same as flash, in reality it isn't exact, but is extremely close. With the EEPROM storing information in a charge of dissimilar silicon and semiconductor material, you don't need a battery to hold the charge. The only thing a sim card needs power for is for the CPU, I/O, RAM and reprogramming the EEPROM, but it does not need power to store data.

 

[guitarguru777]

 

[MarcusGHedwig]

Interesting, thanks a lot for the info guys - see, I always thought RAM was flash memory, as were the old console cartridges that had batteries in them; what's the technical name for that kind of storage, and what are the advantages of it over flash memory? (I assume there have to be some, or else why wouldn't flash memory be used for RAM?)

 

[TheWinterSnow]

Any battery on a memory circuit is used for any volatile memory. However to my knowledge and I just looked it up again, the old game cartridges were ROM of PROM (programmable ROM) with some type of additional EEPROM for saving game data, and again none of those need power as they are non-volatile. So I think you may be asking why then does a BIOS (a ROM) in a computer need a battery? The BIOS chip itself doesn't need power to save the actual program itself, but their is a small amount of memory that is used to store bios settings. IIRC, the memory used is SRAM but is typically referred to as CMOS, since they are using Field Effect Transistors. So that answers your question about what type of memory would be used when there is a battery in the circuit. Older SRAM that was used is called TTL, or Transistor-Transistor Logic, and newer SRAM that is more commonly used today is CMOS, or Complimentary Metal-Oxide Semiconductor.

 

[XnaySaturo]

Interesting, thanks a lot for the info guys - see, I always thought RAM was flash memory, as were the old console cartridges that had batteries in them; what's the technical name for that kind of storage, and what are the advantages of it over flash memory? (I assume there have to be some, or else why wouldn't flash memory be used for RAM?)

Price, size, capacity, speed.

Those 4 are the attributes that justify having all those different types of memory.

 

[slashvanyoung]

Well first off, Flash Memory didn't even exist before 1980 and wasn't commonly used up until the end of the 80s. So DRAM historically became the main RAM on computers (and consoles etc.).

Nowadays, DRAM still serves as the main RAM as it is a lot faster than Flash Memory.

And as TheWinterSnow already said, game cartridges consisted mainly of ROMs, PROM specifically. However, games that featured saving data on NES or SNES cartridges for example DID sport a battery, indicating some sort of volatile memory.

 

[TheWinterSnow]

And as TheWinterSnow already said, game cartridges consisted mainly of ROMs, PROM specifically. However, games that featured saving data on NES or SNES cartridges for example DID sport a battery, indicating some sort of volatile memory.

I read a blog that did x-rays on numerous cartriges over the lifespan of NES and SNES. It made note with some of the pictures that during certain time and even after depending on the manufacturer, either SRAM or EEPROM were used. This was determined by the fact of x-raying a game that you know has data storage features but in the X-ray, does not have a battery.

 

[slashvanyoung]

Ah okay, I never personally owned an SNES but on the games I played and all my NES games that featured saving, there was a battery. It was probably to the end of those consoles lifespans that more manufacturers made use of EEPROMs.

Even some GBA cartridges still came with batteries IIRC.

 

[MarcusGHedwig]

Yeah, it was in Game Boy and GBC carts that I had seen a battery, dunno about the others

 

[TheWinterSnow]

Ah okay, I never personally owned an SNES but on the games I played and all my NES games that featured saving, there was a battery. It was probably to the end of those consoles lifespans that more manufacturers made use of EEPROMs.

Even some GBA cartridges still came with batteries IIRC.

It makes sense to use a EEPROM though because I have heard and seen the tale of someone's battery going out and loosing all their saved files, all because the battery went bad. Then with those cartridges, getting them apart is a pain in the ass because of the stupid proprietary screws they use to take the damned thing apart.

In the end though the CMOS design was cheaper than the EEPROM, where the EEPROM was more convenient for the end user.

 

[slashvanyoung]

Tell me about it. Even as a kid I thought the battery design was a horrible idea. I remember Nintendo having a service for people to send in their cartridges with dead batteries and having them replaced, but batteries usually went bad way after they stopped that. It's happening on more and more of my N64 games these days. There were only few that featured SRAM saving, but it were some of the best.

And I already had to do it twice on my precious golden "Legend Of Zelda" (NES) cartridge. Sucks.

 

[TheWinterSnow]

Tell me about it. Even as a kid I thought the battery design was a horrible idea. I remember Nintendo having a service for people to send in their cartridges with dead batteries and having them replaced, but batteries usually went bad way after they stopped that. It's happening on more and more of my N64 games these days. There were only few that featured SRAM saving, but it were some of the best.

And I already had to do it twice on my precious golden "Legend Of Zelda" (NES) cartridge. Sucks.

There is a special type of SRAM called nvSRAM, which is non-volatile, I think I remember hearing something about it being used in the N64 games. Not sure if it would be cheaper or faster than EEPROM, but it must have been if that was more common.