[En-Nut-Discussion] 128kb Ethernut

[Harald Kipp]

Alastair,

We are already working on this "doped" Ethernut. The
intended memory layout is excatly as you described it.
The size is not fixed, but prices for 512k x 8 SRAMs
are attractive.

The Ethernet Controller will be moved from 8300hex to
upper memory. This way Nut/OS can easily distinguish
between doped and undoped boards.

I started to play around with Cypress PLDs. Directly
using ATmega port lines for bank switching would be
simple. But our IDE MP3 player for example, which is
also running on Nut/OS, uses every single port bit
(IDE, keyboard, LCD) and we want to avoid changing
this or any other existing hardware.

Regarding the OS: In my view this requires a second
set of memory management routines to be integrated
into the API. This way, the application can take
the memory it need and leave the rest to the OS.
Some applications, like Internet Radio, require
large amounts of RAM available for TCP buffering.

The software design is not trivial, though. Think
about thread switching, limited 16 Bit pointers etc.
We more investigations before fixing any details.

Harald