[dragontamer]

Do you take external DDR RAM on an application-class ARM core? You're an MPU.

There's a blurry line sometimes, but Application-class (Cortex A* cores, like A5, A35, etc. etc.) are solidly MPU. Not even close.

[eqvinox]

> Do you take external DDR RAM on an application-class ARM core? You're an MPU.

The actual difference IMHO is the existence of an MMU. (Which is, fdpic/linux-nommu efforts notwithstanding, the general "Linux" condition.)

(Ex.: the SOPHGO SG2000 RISC-V chip comes with integrated DDR3 RAM, but is still solidly an MPU. I believe there are some ARM Cortex-A with integrated RAM too, can't think of any off the top of my head. [Ed.: nevermind, the SG2000 is dual RISC-V/ARM])

[bpye]

Nuvoton have some ARM9 parts with integrated DRAM for example [0].

It’s a little outdated but this blog post is a pretty good overview of the options available [1].

[0] - https://www.nuvoton.com/products/microprocessors/arm9-mpus/

[1] - https://jaycarlson.net/embedded-linux/