NAND vs SDCARD (where is my memory used at?)

m4f1050 · #1 (**permalink**) 09-21-2010, 08:20 AM

Ok, since I had this doubt I figured I'd start a new thread to keep other thread clean.

What I understand so far:

1. NAND (internal memory) is used as "hard drive" and to store OS (what about installed apps?)

2. SDCARD (external memory) is used as "external hard drive" same as internal memory

3. RAM (where OS and APPs load into)

Here are a few doubts I have....

When you boot your phone the OS gets loaded into RAM from the (in our case) SDCARD and when you turn it off this memory gets wiped out because it's volatile?

Is the NAND and RAM shared in some way? Is it partitioned in any way? I remember back in the WM2003 days you could slide and pick where your memory would be used at, but that changed a long time ago. I am guessing that got replaced by RAM/NAND combination?

On HTC website if you check phone specs it gives you 2 different memory sizes (I believe one is RAM the other is ROM) is NAND = ROM?

Is it called ROM but we can "write" to it? It's just a name for it that stores the OS ROM (or should I call it OS installation?) I'm sure there are a few of us that are confused because ROM IS READ ONLY MEMORY written once, never to be written again and again like a "hard drive"...

Examples:
TP2: ROM: 512 MB / RAM: 288 MB
Imagio: 512MB / 288MB (256MB Device + 32MB MSM), SD Card supported
HD2: ROM 1GB; RAM 576MB

mbellot · #2 (**permalink**) 09-21-2010, 09:48 AM

Quote:

Originally Posted by m4f1050

Ok, since I had this doubt I figured I'd start a new thread to keep other thread clean.

What I understand so far:

1. NAND (internal memory) is used as "hard drive" and to store OS (what about installed apps?)

2. SDCARD (external memory) is used as "external hard drive" same as internal memory

3. RAM (where OS and APPs load into)

All correct.

Quote:

Originally Posted by m4f1050

Here are a few doubts I have....

When you boot your phone the OS gets loaded into RAM from the (in our case) SDCARD and when you turn it off this memory gets wiped out because it's volatile?

Not quite "wiped". The android system is loaded into RAM, but the file system remains active (just like WinMo) so you can install programs and adjust settings. These are all saved to the data.img file on the SD card.

Quote:

Originally Posted by m4f1050

Is the NAND and RAM shared in some way? Is it partitioned in any way? I remember back in the WM2003 days you could slide and pick where your memory would be used at, but that changed a long time ago. I am guessing that got replaced by RAM/NAND combination?

Not really. Think of it like a computer. When the PC boots some of its memory is used by the operating system (stored on the hard drive, or in NAND for the phone) gets loaded into memory so it can be run.

Quote:

Originally Posted by m4f1050

On HTC website if you check phone specs it gives you 2 different memory sizes (I believe one is RAM the other is ROM) is NAND = ROM?

Is it called ROM but we can "write" to it? It's just a name for it that stores the OS ROM (or should I call it OS installation?) I'm sure there are a few of us that are confused because ROM IS READ ONLY MEMORY written once, never to be written again and again like a "hard drive"...

Examples:
TP2: ROM: 512 MB / RAM: 288 MB
Imagio: 512MB / 288MB (256MB Device + 32MB MSM), SD Card supported
HD2: ROM 1GB; RAM 576MB

"ROM" is a bit of an incorrect term, and not at all like a hard drive (which is definitely not write once). Part of the NAND is treated like "ROM", but other parts are read/write just like RAM. The difference is that anything stored in RAM goes away after power cycle or soft reset.

Further confusing the issue is that even the portions that are normally "ROM"-like are actually re-writable for things like firmware updates.

m4f1050 · #3 (**permalink**) 09-21-2010, 10:08 AM

Quote:

Originally Posted by mbellot

All correct.

Not quite "wiped". The android system is loaded into RAM, but the file system remains active (just like WinMo) so you can install programs and adjust settings. These are all saved to the data.img file on the SD card.

Not really. Think of it like a computer. When the PC boots some of its memory is used by the operating system (stored on the hard drive, or in NAND for the phone) gets loaded into memory so it can be run.

"ROM" is a bit of an incorrect term, and not at all like a hard drive (which is definitely not write once). Part of the NAND is treated like "ROM", but other parts are read/write just like RAM. The difference is that anything stored in RAM goes away after power cycle or soft reset.

Further confusing the issue is that even the portions that are normally "ROM"-like are actually re-writable for things like firmware updates.

So when we install ANDROID in NAND (or WM ROM in present time) we install in the ROM section and does the OS use part of the ROM (is ROM what we call NAND???) as "hard drive" and store the installed apps or does it store it in RAM? But somehow this RAM doesn't get wiped out when there is a reboot, power off?

Let's split my question....

Is NAND ROM or RAM?

And if RAM is the memory and you load the OS from RAM to RAM, the file system is on RAM but it's not wiped out, that means if we install ANDROID to NAND (or RAM?) we will have less memory for the OS correct?

Where are installed apps stored at?

In comparison, a computer has "memory" and "harddrive"... Is "memory" RAM, "harddrive" ROM or vice versa?

I thought I had this figured out, but not quite. I understand the PC quite well (im a computer engineer and mcpd) but these devices are confusing to me still... In a PC you have what we call harddrive where OS and apps get installed, when you use the PC the os loads into what we call memory.

aronlib · #4 (**permalink**) 09-21-2010, 10:28 AM

Quote:

Originally Posted by m4f1050

So when we install ANDROID in NAND (or WM ROM in present time) we install in the ROM section and does the OS use part of the ROM (is ROM what we call NAND???) as "hard drive" and store the installed apps or does it store it in RAM? But somehow this RAM doesn't get wiped out when there is a reboot, power off?

Let's split my question....

Is NAND ROM or RAM?

And if RAM is the memory and you load the OS from RAM to RAM, the file system is on RAM but it's not wiped out, that means if we install ANDROID to NAND (or RAM?) we will have less memory for the OS correct?

Where are installed apps stored at?

In comparison, a computer has "memory" and "harddrive"... Is "memory" RAM, "harddrive" ROM or vice versa?

I thought I had this figured out, but not quite. I understand the PC quite well (im a computer engineer and mcpd) but these devices are confusing to me still... In a PC you have what we call harddrive where OS and apps get installed, when you use the PC the os loads into what we call memory.

Nand is ROM. Now while essentially ROM is "read only memory" we have the ability to write an new OS on to it.

Ram in a phone is technically the same thing as ram in a PC, it is used for multitasking and have multiple apps open at the same time.

Apps are installed on a partition of the internal memory that is not, Rom.

So basicly we have three parts. Internal memory that's partitioned in 2, one part being ROM "read only memory" that we have the ability to write on to, only when flashing an OS and the other being where we install apps to. and Ram.

**arrrghhh** · #5 (**permalink**) 09-21-2010, 12:31 PM

Excellent explanations by both of you guys. You've been thanked, I was not able to properly describe it

m4f1050 · #6 (**permalink**) 09-21-2010, 04:30 PM

Gotcha.

"ROM" = partitioned where OS resides and a writable partition where programs get installed.
"RAM" = what phone uses to operate.

Now my question is....why when I install apps my "RAM" decreases? Or is is "RAM" the one that has the 2 partitions and ROM only gets the OS installation?

**arrrghhh** · #7 (**permalink**) 09-21-2010, 04:52 PM

Quote:

Originally Posted by m4f1050

Gotcha.

"ROM" = partitioned where OS resides and a writable partition where programs get installed.
"RAM" = what phone uses to operate.

Now my question is....why when I install apps my "RAM" decreases? Or is is "RAM" the one that has the 2 partitions and ROM only gets the OS installation?

RAM is only used for running programs/services... I mentioned this before but you probably missed it.

RAM is basically a place for programs to store information that it needs to access quickly - as RAM is much faster access than a hard drive, NAND, etc. So the OS uses RAM as a buffer so to speak - between the processor & storage device.

So this is a place for the system to store things temporarily - you can't store things directly on RAM, as it would get cleared out on device shutdown/restart.

m4f1050 · #8 (**permalink**) 09-21-2010, 05:11 PM

Quote:

Originally Posted by arrrghhh

RAM is only used for running programs/services... I mentioned this before but you probably missed it.

RAM is basically a place for programs to store information that it needs to access quickly - as RAM is much faster access than a hard drive, NAND, etc. So the OS uses RAM as a buffer so to speak - between the processor & storage device.

So this is a place for the system to store things temporarily - you can't store things directly on RAM, as it would get cleared out on device shutdown/restart.

So that in my dictionary is a "ramdisk" does Android use a Ramdisk? It could possibly explain why...

**arrrghhh** · #9 (**permalink**) 09-21-2010, 05:28 PM

Quote:

Originally Posted by m4f1050

So that in my dictionary is a "ramdisk" does Android use a Ramdisk? It could possibly explain why...

Uhm... It uses RAM, perhaps you're thinking of swap? In Windows this is called a page file - basically it slices out a piece of the hard disk to use the same way that RAM is used - but it's supposed to be used very sparingly - in Linux systems it's only used when you run out of RAM. Windows... it's a little more fuzzy.

m4f1050 · #10 (**permalink**) 09-21-2010, 05:45 PM

The term ROM is wrong in a way..that's what threw me off to begin with. I now see it different and understand it. I hope others that had the same doubt can understand it as well, it will eliminate questions when it comes to switching the os to NAND and worry for nothing. NAND is a faster memory than SDCARD and booting times will be less once we get ANDROID on NAND..