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

[tiger2wander]

Hi guys,

IMO, Phone, SmartPhone, PPC & many kind of portable devices has a difference hardware design compare with PC. As many devices has SoC or Storage on Chip is a way to combine all chipset and storage into only one board to make it small, fast and decrease it's cost to product and also make it faster than use cable like IDE, PATA, SATA like in the PC. By the way Storage on phone can be divided by logic way, not hard way so it can get more flexible (It has been partitioned like our HDD: boot partition has Bootloader, some bytes used as SPL like Master Boot Record on HDD, OS, EXT ROM, OEM, XIP ....). In the summarize we can imagine it like:
- ROM: is read-only-memory as it's name but usually modern ROM are kind of PROM, EPROM or EEPROM (*) so it can be re-writable such as BIOS on the PC (You can update your PC BIOS). But PROM, EPROM or EEPROM has small limit number of write in it's life cycle so it was used to store factory data or Stock ROM then that data will be use to restore to factory anytime you get error on your own runtime version (I will describe later).
- NAND is a kind of Flash memory like SSD and USB. So it can be use to store data with high rate of IO to make we have fast OS running on it. IMO it has divided to 2 parts using logical way instead of hard way. 2 parts are Internal Storage & Program as called in WinMo Memory settings (You can find it in Settings -> System -> Memory). Internal Storage is use to store user data like: installed applications, application data, your images, video, book stored in "My Documents" .... so this part has been map with ROM. BTW all files and directories in this part by default are map with files & directories in ROM so you can see it almost like ROM structure right after Flash a new ROM, then you go to modify (delete, override) any file or directory in this part then it will write to "Internal Storage" and marked override flag (Caused of you can restore any override ROM's file by using some application like: SKTools from SK Software to find overrided file and restore it from ROM). The second part is use as RAM or "Program" as WinMo call it.

Is my logic correct? let's comment out

[natemcnutty]

Originally Posted by arrrghhh

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.

Android can use a RAMDisk, but I'm with Arrrghhh on not being sure exactly what you are describing.

In Linux, you have compcache module which sections off a chunk of RAM to use as a RAMDisk. We have the drivers and everything available in the kernel to use on the XDAndroid builds, but I'm not sure if it is actually used or not. As far as swap/pagefile goes, that is virtual memory that should only be used when the system needs to free up memory blocks but needs to retain the information it is trying to clear out.