7 Feb
2012
7 Feb
'12
4:37 p.m.
On 02/07/2012 05:39 PM, Ethan Dicks wrote:
Yes, UZI unix, Look it up in google.
It's not impossible though you might have a hardware abstraction to
deal with recursion and addressing. But it will not be pretty.
Think of C as a macro assembler. The PDP-8 was generic that it could do
all of the possible tasks. The compiler would have to be smart but they
write
in C for PIC micros.
Its likely doable but it would take work. Keep in mind that an -8 maxes
memory at 32Kwords. that means bigger will have to have a mechanism
for swapping to storage.
Keep in mind the Z80 did not ahve many of the addressing modes of C.
On Tue, Feb 7, 2012 at 12:51 AM, Cameron
Kaiser<spectre at floodgap.com> wrote:
11/23 (KDF11A not KFD11B or later 11/23) with 256K and a RL02 running
unixV6.
> So, does anyone have a record for oldest or
weakest computer running Unix?
The oldest/weakest I've personally run UNIX on
was an 11/24 w/dual
RL02 (10MB each) and 2MB of RAM. It's far from a record. If I can
find an affordable EAE for my PDP-11/20 and figure out how to sub the
swap disk with something other than an unobtanium fixed-head disk, I'd
run it there, but that's a long-term project.
> The Z80
definitely did it.
UNIX? Really? Or just something with a Bourne-like command
line?
> I
don't think the PDP-8 could.
I gotta say that I don't think so either.
> I've
been trying to figure out if the PDP-8 could handle C, and
> the answers I get range from "I don't know" to "Definitely
not".
I am not aware of a C compiler for the PDP-8, but I think it would be
exceedingly difficult to write one if were possible at all (I've done
a lot of system and embedded code in C and debugged it in assembler,
so I know a bit about the syntactical mapping that goes on with C
abstractions to the instruction sets of MC68000s, VAXen, PDP-11s,
etc).
> Something
I'd really like to see is a Z-machine running on the PDP-8.
I would like that
too. I've even thought a lot about it. IMHO,
anyone who does it will be writing the Z-machine in PDP-8 assembler,
just like what was done for the Z-80 and the 6502 for 1970s and 1980s
micros. I _think_ the Mac Z-machine was the first written in C, but I
could easily be mistaken on that. I know there were official
Z-machines written in C for the Mac and the Amiga, and probably the
later ones on the PC (not sure about the early v3 interpreters for
DOS).
I like Frotz. Frotz is huge compared to the 6K-8K
early 8-bit
interpreters. It gets more dicey trying to ask a 12-bit machine with
4K pages to emulate a 16-bit virtual machine.
You can hide all that in the virtual
machine. You pay the price for
speed and there isn't much there.
I would consider it a
win if one could fit the Z-machine code in 2 fields with enough space
left over for a 2-page system handler and a 1-page line printer
(SCRIPT) handler, using any memory above 8K for object data and game
file buffers. Three fields seems plausible.
Also consider swapping memory as back
when for large PDP-8
programs that was the norm. Something like RS08 disk was the
best game for that as you could spool memory to disk or back at
data break rates (around 6us/word).
A few years back, I
assisted with a modern from-scratch Z-machine effort for ElfOS on the
1802 (that I was showing off at an early VCFmw). On a 32K Spare Time
Gizmos Elf2000, once the interpreter was loaded and the object tables
were loaded, there was very little room to buffer the game - I think
it was on the order of 1-3 512 byte disk blocks. You can fit a v3
game and interpreter in 32K, but to do it in less would probably
require a read-write virtual memory scheme on the object data
(fortunately, a full boat on a PDP-8 is 32K 12-bit words not 32K 8-bit
bytes - that helps too).
That and if you do text in six bit ascii you get two cars to a word.
Strangely enough, I was just thinking about a 12-bit
Z-machine this
week. Anyone out there have 12-bit coding experience and have time to
answer a few questions about OS/8 and file interchange from the 8-bit
outer world?
Some here, not a lot as I've not run OS/8 in a long time. FYI
a suitable dev system would be a DECmateII or III running OS278.
The biggest thing to watch for in PDP8 code is recursion as you
need a software stack and handler to preserve data/addresses.
The DECmates had the 6120 and that implemented IOTs to create
a address and data stack( hardware can be built to do that in
any omnibus 8). The unique PDP-8 IO made doing things like that
more common than would be guessed.
Allison