Original document by Fred Martin
Updated by Randy Sargent, July 29, 1994

>       I have a small question related to the boards used at the MIT
> around the Motorola 68hc11: can you explain me what are the main differences
> between the miniboard and the 6270 board, from the hardware and software
> points of view? For example, I have the impression that the 6270 is
> easier to program since the interactive C-compiler seems to be ready to use.

Here are the primary differences between the two:

HARDWARE-

The Mini Board has no external memory, so it's limited to the 2K
internal EEPROM of the 'hc811e2 version of the chip.  There are
drivers for 4 motors, and the rest of the 6811 pins are brought out to
headers.

The 6.270 board has 32K of RAM, and also comes with an expansion board
giving you 2 more motor outputs (for a total of 6), and lots more
analog sensor inputs (using a multiplexer chips).  It also has an LCD
screen.

SOFTWARE-

Because of the memory limitations, the Mini Board is best programmed
in assembly language, or a limited version of C (e.g., Dunfield's
Micro-C system [a $100 product], or Richard Man's free icc11
compiler).

The 6.270 board has a custom software environment, Interactive C,
which is a multi-tasking, interactive version of the C language.  It's
a pretty cool system.  A free version of Interactive C is available from
cher.media.mit.edu in pub/interactive-c.  Sources are available.

SUMMARY-

The Mini Board is a lot easier to get started with.  The board itself
is smaller, has many fewer chips, is easier to build, and is easier to
debug.  If you have a DOS system, the Micro-C environment is quite
simple to use, and while not interactive or multi-tasking, is
functional.  You will be limited by the 2K of memory, however.

The 6.270 board is great once you get it working, but will be a bear to
debug if you have bad solder joints or the like.  It takes 10 to 12 hours
to build.  If you want to go with the 6.270 board, try to buy a completed
and tested board; P.K. Oberoi (spedhead@mit.edu) does provide this service.
Interactive C is a lot of fun to use, and the 32K of memory is enough to do
a significant project.

Another thing to keep in mind regarding Interactive C is that it
cannot build ROM-able applications.  There were several design choices
made during its development which require that it run from RAM.  This
means that you can't build serious applications with it, since RAM
isn't suitable for something that has to really work for a long time.
For experimentation and general playing around, though, IC is great.