Re: Minimum RAM size requirement of the MIPS port

[Hakurei Reimu <reimu%sudomaker.com@localhost>]

Hi Simon,

Thank you for the information!

But I forgot to mention a thing - the executable code in a MCU can be
executed in place (XIP) on flash storage, there's no need to copy them
to RAM like on a desktop PC. This chip can support at least 32MiB of
external QSPI NOR flash storage.

So do you know how much RAM the kernel will be using at runtime
(stack, heap, pcb, etc) ?

Regards

Simon Burge <simonb%netbsd.org@localhost> 于2021年11月19日周五 下午1:51写道：
>
> Hi Hakurei,
>
> Hakurei Reimu wrote:
>
> > Hello everyone. I want to know the minimum RAM size requirement of
> > running latest NetBSD on a MIPS machine.
> >
> > I want to port latest NetBSD to Microchip PIC32MZ, which is a powerful
> > MIPS32r5 microcontroller with FPU, MMU, L1 Cache and 512KB of RAM.
> > Since it's capable of running the original 4.4BSD (See
> > https://hackaday.com/2016/01/04/litebsd-brings-4-4bsd-to-pic32/), and
> > NetBSD is 4.4BSD's closest relative, I want to know if it's possible
> > to run NetBSD on it.
>
> The smallest MIPS kernel I have laying around is for MIPSSIM which
> has only two or three device drivers and is far larger than your total
> RAM size:
>
>            text    data     bss     dec     hex filename
>         3771444  719632  103872 4594948  461d04 MIPSSIM/netbsd
>
> If I trim out most optional things, this only gets down to:
>
>            text    data     bss     dec     hex filename
>         1995244  101392   58864 2155500  20e3ec MIPSSIM-small/netbsd
>
> which is still far too large.
>
> I would think 16MB of RAM would be an absolute minimum to do much more
> than boot with NetBSD.  32MB should be reasonably usable for a minimal
> system.
>
> Looks like the compiled kernel for LiteBSD is around 500kB.  Impressive!
>
> Cheers,
> Simon.