RAM 是指运行内存，
ROM 指存储大小
emmc = nand flash + 控制器 + 封装
emmc 功能
1、存储以及取得NOR flash 的开机功能，
2、最大好处是，手机厂商不需要因为nand flash 供应商或者不同 制程世代而重新设计规格
3、不需要处理 nand flash 相容性和管理问题
4、手机客户只要采用emmc 晶片，放入手机
eMMC 分区表
| Partition# | Name# | Size# | Strat LBA-End LBR | Description# |
| 0 | MBR & GPT | 0x00000000-0x000000FF | Master Boot Record and GUID Partition Table | |
| 1 | x-loader(MLO) | 256KB | 0x00000100-0x000001FF | First stage bootloader |
| 2 | bootloader(u-boot.bin) | 384KB | 0x00000200-0x000005FF | Second stage bootloader |
| 3 | misc | 128KB | 0x00000600-0x000006FF | Reserved.This partition can be used for internal purpose |
| 4 | recovery (zImage + recovery-ramdisk.img) | 8MB | 0x00000A00-0x000049FF | recovery partition |
| 5 | boot (boot.img = zImage + ramdisk.img) | 8MB | 0x00004A00-0x000089FF | Partition contains kernel + ramdisk images. |
| 6 | system (system.img) | 256MB | 0x00008A00-0x000889FF | android file system |
| 7 | cache (cache.img) | 32MB | 0x00088A00-0x000989FF | Partition will be used to store application cache |
| 8 | userdata (userdata.img) | 32MB | 0x00098A00-0x000A89FF | Partition contains userdata supplied by oem vendor like configuration files,utilities etc.. |
| 9 | media | Remaining | 0x000A8A00-0x00762761 | Partition contains media files; supplied by oem vendor |
MTK分区表存放位置：device/mediatek/build/build/tools/ptgen/xxx/xxx.xls ptgen.pl文件会把xls文件解析成xxxAndroid_scatter.txt放在out/target/product/xxx/中 mtk的flashtool工具会读取这个文件把相关的镜像烧写到rom中。