Date   : Mon, 04 Jul 2005 11:43:47 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Small-C v0.73

On Mon, 2005-07-04 at 00:47 +0100, Jonathan Graham Harston wrote:
> It feels so wierd issuing commands from a '$' prompt on my Beeb...
> Unix Z80 Implementation already exists, I've already got a 'ls'
> command, I'm so tempted to put together a BBC 6502 Unix system...
> BeebNix? BeeNix? Bunix?

You know, that'd be pretty nice... (I like Bunix!)

Doubtless it's possible, apart from the obvious lack of memory
management. I wonder if some simple MMU hardware could be bodged and
hung off the Tube port - but if not present the system could just run
without and with no memory pretection.

Getting OS core, filesystem driver, shell, network stack, and then any
running utilities on top of that might be tricky though given the memory
available. 

uIP's an optimised  TCP/IP stack for 8 or 16 bit machines - idea of
memory usage is here:

  http://www.sics.se/~adam/uip/size.html


... so a shade over 7KB for a useful implementation. Mind you, that's
with a built-in web server, which in the case of a beeb implementation
would be a seperate process.

Shell - I don't know, a basic shell that was little more than a program
launcher and kept track of environment and current directory (and had no
built-in stuff like ls) could be pretty small I suppose.

Filesystem overhead might be significant I suppose if you want a
reasonable fs that doesn't have low limits for files per directory etc.
My old NCR Unix box survives happily with 15 character filenames;
anything less might get difficult though.

Not sure what kind of overhead you'd have for a /dev structure and
allowing programs to read/write devices representing the disk, console
etc. but I'd assume it'd be possible. It's not really unix without
anyway :-)

Maybe a Master's the way to go for starters so you have the extra RAM,
then shift it over to the B once it's optimised enough.

If you want to chuck ideas around on this then feel free - I'm a bit
rusty on this kind of stuff as it's a good few years since I did any OS
development though!

cheers

Jules