Flash Drives

[Old Dad]

MT's thread about the Garmin untimately led to mention of flash drives and raised a question in my mind: What exactly ARE flash drives composed of?

I realize that there will be a chip or two for support purposes - USB interface, clocking (sync) and so forth. But what I'm asking bout is the actual storage media itself. Is it a chip or two that consists of a huge string of NAND gates? Like CMOS or NMOS or TTL gates? In essence, something akin to a really big HUGE register in a CPU? Just remember that I'm an old guy who still thinks in terms of discrete components even when they've been shrunk to microchip size. The functionality is still identical to the original full-sized transistors, resistors, etc. In other words, a flip-flop is still a flip-flop.

If so, they would not be subject to static magnetic fields (a question that was posed in that thread) but *would* be subject to a strong VARYING magnetic field which could induce voltage transients inside the chip(s).

And if the structure is as I'm guessing (what I just described above) it would also explain their long service lives and eventual failure since transistors and other components will "give up the ghost" at some point in time.

Anyone know if my guess is correct - or what the real answer is?

[drew]

MT's thread about the Garmin untimately led to mention of flash drives and raised a question in my mind: What exactly ARE flash drives composed of?

I realize that there will be a chip or two for support purposes - USB interface, clocking (sync) and so forth. But what I'm asking bout is the actual storage media itself. Is it a chip or two that consists of a huge string of NAND gates? Like CMOS or NMOS or TTL gates? In essence, something akin to a really big HUGE register in a CPU? Just remember that I'm an old guy who still thinks in terms of discrete components even when they've been shrunk to microchip size. The functionality is still identical to the original full-sized transistors, resistors, etc. In other words, a flip-flop is still a flip-flop.

If so, they would not be subject to static magnetic fields (a question that was posed in that thread) but *would* be subject to a strong VARYING magnetic field which could induce voltage transients inside the chip(s).

And if the structure is as I'm guessing (what I just described above) it would also explain their long service lives and eventual failure since transistors and other components will "give up the ghost" at some point in time.

Anyone know if my guess is correct - or what the real answer is?

Hey Old Dad,

The majority of flash storage in consumer devices is NAND flash, which is just as you say, a big array of NAND gates. The difference is that they are able to hold their state without a continuous source of power. There is 'NOR' flash as well, but this isn't nearly as popular. I don't know the details of their implementation, or the pros and cons of either type.

Drew

[rickharris]

Ok Also an oldi I will have a stab here.

Flash drives evolved from PROMS Programmable Read Only Memory. Originally the 1's and 0's were burned inti EPROMS by breaking what amounts to a fuse link. A one time operation.

EPROMS Erasable programmable read only memory - Using a technology where the data retained in the could be erased by the application of a high energy source - strong Ultra violet light was the main source. Many PROMS are just EPROMS in a black casing.

Then EEPROMS arrive electrically programmable etc.

These devices are developments of Field Effect Gates where electrons can get trapped in the gate and will continue to switch the FET on or off. giving a 1 or 0.
The state is read by applying a change state signal if it changes it was say a 1 if no change then it was a 0 (the original state is then rewritten.)

Flash memory is very similar except an EEPROM usually has a larger area because each gate is individually erasable and so needs a driving transistor. Flash memory is usually erased in blocks and so needs fewer driver transistors.

Beyond that as far as I know it is most certainly magic!

[Elefino]

Ok Also an oldi I will have a stab here.

Flash drives evolved from EPROMS Electrically Programmable Read Only Memory. Originally the 1's and 0's were burned inti EPROMS by breaking what amounts to a fuse link. A one time operation.

Then EEPROMS arrive electrically programmable etc.

These devices are developments of Field Effect Gates where electrons can get trapped in the gate and will continue to switch the FET on or off. giving a 1 or 0.
The state is read by applying a change state signal if it changes it was say a 1 if no change then it was a 0 (the original state is then rewritten.)

Flash memory is very similar except an EEPROM usually has a larger area because each gate is individually erasable and so needs a driving transistor. Flash memory is usually erased in blocks and so needs fewer driver transistors.

Beyond that as far as I know it is most certainly magic!

I thought EPROM meant Erasable Programmable Read Only Memory

[rickharris]

your right joel Memory skipped a link there - HAD to look it up - am I getting old like you ! i have corrected the original post.