Flash Memory - Tilted Forum Project Discussion Community

FloydianOne · 08-12-2005, 07:03 PM

I was reading this article on wiki about Flash Memory and had a question about the two types of memory - NAND gate and NOR gate.

http://en.wikipedia.org/wiki/Flash_Memory

It says that the NAND Flash like smartmedia cards uses a sequential access I/O interface. I must not know exactly how sequential access works because I always thought of it in the "tape drive" example kind of way. Meaning to get to one part of data you had to go through all the data before it.

Can someone give me a clear example of how I can see this in real life? Are computers just so fast now days that you dont really see a difference in seek times etc? When i look at say digital photos on my smartmedia card, I can point to a specific file and delete it.... how is this not random access.

I must be confused, thanks for any input.

bermuDa · 08-12-2005, 10:01 PM

I think this link might be helpful, it has a point-by-point comparison between NAND and NOR architectures.

http://www.linux-mtd.infradead.org/a...tech/nand.html

oberon · 08-13-2005, 06:53 AM

Gates aren't types of memory, they're building blocks for logic circuits. Memory happens to use them. NAND/NOR gates are quite simple by themselves, but using them in large blocks can get complex. Usually people try to use only one type of gate because it simplifies routing & placement of signals in a logic circuit.

To answer your question, tape drives are sequential like the NAND memory architecture. But they are many times faster since they don't have moving mechanical parts like tapes, so for small array sizes, they are effectively random access. Also, something else to keep in mind is that deleting a file on a filesystem merely involves removing the file's entry from the filesystem table.. nothing more. And presumably the filesystem table is stored at or near the start of the memory in a flash memory chip. And there are many ways to 'cache' changes so they appear instantaneous to a user but actually happen over a slightly longer period of time than they appear to be. The wonders of modern computers.

08-12-2005, 07:03 PM	#1 (permalink)
FloydianOne Crazy	Flash Memory I was reading this article on wiki about Flash Memory and had a question about the two types of memory - NAND gate and NOR gate. http://en.wikipedia.org/wiki/Flash_Memory It says that the NAND Flash like smartmedia cards uses a sequential access I/O interface. I must not know exactly how sequential access works because I always thought of it in the "tape drive" example kind of way. Meaning to get to one part of data you had to go through all the data before it. Can someone give me a clear example of how I can see this in real life? Are computers just so fast now days that you dont really see a difference in seek times etc? When i look at say digital photos on my smartmedia card, I can point to a specific file and delete it.... how is this not random access. I must be confused, thanks for any input. __________________ Fight apathy! ..... or dont.

08-12-2005, 10:01 PM	#2 (permalink)
bermuDa don't ignore this--> Location: CA	I think this link might be helpful, it has a point-by-point comparison between NAND and NOR architectures. http://www.linux-mtd.infradead.org/a...tech/nand.html __________________ I am the very model of a moderator gentleman.

08-13-2005, 06:53 AM	#3 (permalink)
oberon Quadrature Amplitude Modulator Location: Denver	Gates aren't types of memory, they're building blocks for logic circuits. Memory happens to use them. NAND/NOR gates are quite simple by themselves, but using them in large blocks can get complex. Usually people try to use only one type of gate because it simplifies routing & placement of signals in a logic circuit. To answer your question, tape drives are sequential like the NAND memory architecture. But they are many times faster since they don't have moving mechanical parts like tapes, so for small array sizes, they are effectively random access. Also, something else to keep in mind is that deleting a file on a filesystem merely involves removing the file's entry from the filesystem table.. nothing more. And presumably the filesystem table is stored at or near the start of the memory in a flash memory chip. And there are many ways to 'cache' changes so they appear instantaneous to a user but actually happen over a slightly longer period of time than they appear to be. The wonders of modern computers. __________________ "There are finer fish in the sea than have ever been caught." -- Irish proverb