What kind of memory does the device memory of modern smartphones belong to? Is it SRAM or DRAM, or some other kinds of memory? I think the device memory of smartphones is an analogy to RAM in personal computers (in terms of usage), except the former cannot be easily added or installed by user, while SD card of smartphones is an analogy to hard disks in PCs. So, is the device memory the same type of memory as the RAM in PCs?

p.s. Sorry if this question is off-topic. I think this is a question about computer organization and architecture, so it seems best suited to electronic engineering.

  • \$\begingroup\$ After some thoughts, it seems like the device memory should be some sort of permanent, non-volatile memory. Otherwise when the phone is switched off, the apps installed will be lost. So is the device memory some sort of fast Flash memory? \$\endgroup\$ – GreenPenguin Nov 23 '16 at 7:38
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    \$\begingroup\$ Phones have both flash (NAND flash) and RAM (SDRAM, usually LPDDRx). Apps are installed in flash (equivalent of the hard drive on a computer), but the CPU is working on RAM, because working directly on flash is impossible (it would be too slow and it would kill the flash quickly). \$\endgroup\$ – dim Nov 23 '16 at 8:06
  • \$\begingroup\$ @dim Thanks, does this mean the flash memory provided internally by the phone is a different kind of flash memory from the SD card that normal users are allowed to install? \$\endgroup\$ – GreenPenguin Nov 25 '16 at 8:32
  • \$\begingroup\$ No, it's the same kind of flash. The difference is in the way it is accessed: the flash in the phone is directly connected to the CPU using a high-speed bus. The flash in the SD card is connected to a controller embedded in the SD card, to bridge between the SD protocol and the flash memory, and then there is another controller within the phone to bridge between the SD protocol and the CPU (usually, this bridge is embedded in the CPU itself). But it's the same. Now, the phone OS may not allow you to do the same things on the SD vs the phone flash, but that is another problem. \$\endgroup\$ – dim Nov 25 '16 at 8:42

All of the above in some form or other.

The RAM listed on the specifications will be DRAM of some sort. Very similar to the RAM in a desktop PC only optimized for low power rather than raw speed.

There will also be some SRAM in the form of the CPU L1 and L2 cache, since that is determined by the CPU used rather than something the phone manufacturer can change it's not normally listed on the specs.

And then there will be NAND FLASH providing the main storage, this is like an SSD hard drive in the PC.

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    \$\begingroup\$ Low power DDR, usually 3 or 4. Running at high speeds to support the GPU and display. Sometimes as package-on-package. \$\endgroup\$ – Sean Houlihane Nov 23 '16 at 9:17

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