Re: 68030 SBC project ideas

[lynchaj <lyn...@yahoo.com>]

Hi

Regarding the 680x0, IMO a built in MMU is a requirement for any hope
of a NetBSD or Linux variant.  In theory we could use a 68030 but
those seems to be unobtainium now.  Some of the 68040s have MMUs and
would work.

However you can see the cost of this project is escalating rapidly.
Even a simple 60 square inch 2-layer pre-stuffed board (assuming we
are going the MC68360 route or some other SMT major component) even
the PCBs start to be in the $100 each range.  ($20 for a bare PCB +
$30 for the MC68360 + stuffing fees + shipping etc).

I am not sure of the availability of eBay MC68040 CPUs.  Some are in
the $40 range but is that a sustainable supply or just a onesie/twosie
deal?  Commercial suppliers of MC68040 according to findchips.com is >
$200 each even for SMT variants and that's non-viable IMO.

There are some cruel economics we are going to have to work out to
make this project viable.  $300 units (PCB + CPU) before you've even
added your own components is out of the reach of most hobbyists I
think.

In spite of their awkwardness, the Intel camp definitely won the
hardware price wars of the 1990's and this may be the reason.
However, I am not seeing may graceful solutions for 80486 like the
MC68040/MC68360 combo either.  The 386EX looks interesting but it is a
386SX variant and looks to be limited to 16MB physical address space
which is a deal breaker for an advanced OS.

We are not constrained to MC68040 though.  There may be other
integrated solutions out there.  How about ARM or AVR?  The PIC folks
recently adopted the MIPS32 architecture.  Are they possibilities?

Thanks and have a nice day!

Andrew Lynch