26 Aug
1999
26 Aug
'99
10:06 a.m.
I suggested to some folks, off list, that perhaps DEC
should make the
PDP-11 architecture "open source" in the sense of allowing anyone to
produce PDP-11 capable processors but was told that Mentec has purchased
the rights to the PDP-11 architecture from DEC. What's up with that? True?
False? Kind-a true? (I know Mentec sells PDP-11 compatible computers)
Mentec sells several different kinds of PDP-11 compatible computers,
some of them based on the DEC/Harris J-11 chipset, others based around
custom FPGA's. See http://www.mentec.com/ for a rundown.
Other companies have made drop-in PDP-11 replacements over the years, too.
QEI (based in MA) makes drop-in upgrades for 11/34's, 11/44's, and
11/70's, and Setasi (in Florida) makes drop-in upgrades for 11/70's.
I don't think there's any legal impediment to picking up a PDP-11 processor
handbook and implementing your own hardware design of the architecture.
(Just as there's nothing stopping you from building a PC-clone motherboard
or a x86 CPU based on published specs.)
In the end, you'll have to be sure that you aren't stepping on anybody's
patents, of course.
Given the complexity of the 11/70 CPU it should be
possible to put the
entire thing inside a relatively inexpensive FPGA these days.
The faster Mentec boards are heavily built around FPGA's, they are
certainly one common way to go for such things.
Given
something like NetBSD that is already multi-architecture aware, that would
make it possible to have an open source OS running on it.
I'm not sure that NetBSD is necessarily the way to go. It hogs memory
like crazy (not something you want to do in the 16-bit virtual
address space of an -11), the standard compiler (gcc) is a real CPU-eater
compared to "native" compilers, and changes to the predominantly Intel-based
sources take a long time to get "fixed up" for the less common architectures.
Heck, the current Vax port is actually less functional (in terms of
stability and hardware support) than it was three years ago.
OTOH, for $100 you can get a Unix source license ( see
http://minnie.cs.adfa.oz.au/PUPS/index.html ) and run 2.11BSD on your
hardware, which gives you just about everything you could want from a
modern Unix (including networking) that will actually fit. And it
doesn't use gcc - that's a *real* advantage on an -11!
Yes, I have run RT-11, RSX-11, and 2.11 BSD on systems that didn't
have a single DEC hardware component in them. (For example, a Mentec
M100 CPU and Andromeda disk controller in a third-party Q-bus backplane.)
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
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