Hello ELKS mans,
first I must excuse for my english. Because it is not my native
language, there are possible errors in my letter. I will be
pleasured for any correction which help me improve my english.
In last saturday I was looking for anything about null
modem cable in my old materials. I found it and make a nice
one, but this is not what I want talk about. I found printed
copy of old ELKS web page dated to september 1997. Some
citation:
The initial target for ELKS is the Intel 8086
processor family. Other targets like Z80,
680x0, 683xx and MIPS R4xxx embedded processors
or the 6502 will be added later.
An 8/16bit processor kernel is badly needed.
Backporting ELKS to machines like the PDP-11
that was V7 binary compatible has a would be
lots of fun.
I was thinking much about it, ELKS, and small embeded
computers. As I know, there is no suitable hardware. You can
say that there is a pile of old PC's (are not small), someone in
this list was talking about embeded controller based on 80186
and someone else about Z80 processor which is not supported now
(all these have lack of some sort of memory protection). If you
know anything else I don't, let me know about it.
Imagine how you protect your system before crackers, and of
course before yourself. The cracker problem you can resolve
with some pain. Do not connect your small system to network of
any type and physically protect it before unauthorized access.
But you can not protect it before yourself. One badly written
command in your program can cause a kernel goes to heaven or
hell (you can choose). See I do not write one malicious command
but one baddly written command (I have a typo on my mind).
I thing that there are two ways to resolve this problem.
First way is hardware way. A construction of cheap
hardware with protected mode and memory protection scheme is
needed. This one is big problem, how many 16-bit processors
with protected mode, and memory protection you can use. I know
about I80286, J-11 (LSI-11, DCJ-11, K1801VM1), if you know more,
let me know. Are these processor yet on market? I think no.
But we can design our own processor, and model it in FPGA
(Xilinx or other). This needs much work and advanced experience
in hardware projecting and construction.
Second way is software way, its way of emulators. You can
emulate some hardware architecture which meet your needs. Bad
news is that this cost much in speed. Slowdown need not be to
big, not as you expect. And well designed hardware may have
some advantages in memory savings You can code a often used
sequences to one simple instruction and save much space in code
segment.
If you begin with software emulator you may in future build
an hardware which use same instruction set and thus save all
previously done work.
Are you asking why am I writting this? A month ago I found
an emulator of PDP-11 minicomputers family. I also found a
couple of software for it including old unix V5, V6, V7. And
for some bucks you can get an License for ancient unix source
code. And get a BSD2.11 unix with source code to. Then I begun
thinking about hardware emulator and also porting ELKS to this
hardware.
May be its only dream which don't come to reality, but nice
dream.
I must say that I'm not hardware engineer, and have no big
skills in this area.
Will be there any interest to make some "research" in that way?
Radek Hnilica
E-mail: [EMAIL PROTECTED]
http://www.linuxfan.com/~radek_hnilica
