Paul Koning wrote:
>> The 1971 Unix Programmer's Manual mentions their 11/20 had 24 KB
>> (surely KW?) memory rather than 28KW.
> I would assume kW. In the PDP11 world we didn't normally speak of
> bytes or kbytes, certainly not for memory and often not elsewhere either.
The PDP-11 Unix source:
orig = 0
core = orig+40000 / specifies beginning of user's core
ecore = core+20000 / specifies end of user's core (4096 words)
So: 40000= 16KB for the kernel, 20000= 8KB for the user program.
According to this page that Dennis Ritchie wrote, the original PDP-11
they used was indeed an 11/20 but it was before there were PDP-11 model
And, of course, the PDP-7 Unix development came before the PDP-11 version :)
Steve Malikoff wrote:
> It states that their 11/20 had a KS-11 memory management unit, was that
> mandatory for running v1 Unix on an 11/20?
I case-insensitively grepped for 'ks.*11' in the Github repository here:
and I didn't see a mention.
> The 1971 Unix Programmer's Manual mentions their
> 11/20 had 24 KB (surely KW?) memory rather than 28KW.
28KB is right. The simh.cfg from the repo says:
set cpu 11/20
set cpu 32K
Is anyone willing to sell me a few Teac FD55-GF or -GFR floppy drives (PC
5.25-in high density) for less than eBay prices? I want to experiment with
modifying them to read Apple Twiggy diskettes, primarily by adding a
microstepping driver for the head positioning.
I specifically want Teac drives because there are reasonably good service
manuals on them, and I don't want to deal with multiple brands of drives.
The handwritten labels on the Twiggy diskettes I recently acquired make it
appear that they were used for prerelease Lisa development. I will be
getting more of them in a few weeks, from the same source.
Hello all, I have been a student of computer history for years but have
only learned how to use classic machines vicariously through emulation. I
would really like to get my own classic computer but I don't know where to
begin. For one, I am on a very limited income and two I don't have a lot
of space and finally I don't have much knowledge on the finer points of the
older hardware i.e. terminals networking, etc. I would really like a
Vaxstation but I have also considered a '90s workstation such as an SGI
Indy or a SparcStation. I am pretty fluent in both VMS and Unix so any of
those would work. So where do I look besides e-Bay? I see some available
here but none near me. I'm in the Detroit area. Any advice would be
appreciated. I do know that I do now want a Mac or old PC. I would like
something more exotic. (Although it might me neat to own a Rainbow.)
I have been asked to dump the ROM contents out of the MC6801 in the
Ericsson PC keyboard to get the MAME emulation fully working. The guy that
is doing the emulation says this is the only thing missing and would be
nice if I could help him getting it finalized.
It is supposed to be quite easy. Put the MC6801 in test mode 0 and provide
RESET vectors for an external EPROM that has a program that dumps the
contents. Maybe in Intel HEX over the serial port. Should be quite straight
forward. But I have thousands of other things to deal with so if someone
already made such a small program I gladly use it instead of making my own.
Even though I done some 6800 and 6809 assembler once upon a time, it was 30
years ago, so I imagine it will take some time to get it working.
Is there anyone that already done this?
I bought a large package of DEC gear last year and it came with a PDP
11/15. I have no need for this classic, and put it on the list. A few
people responded, but because of my problems, I never followed up with
For those who responded, I apologize for dropping the ball. If anyone is
interested in it, please contact me off list.
BTW, I have started on pulling a few things out of the warehouse.
> It's a VAXstation II/GPX. I'm trying to install VMS 5.5 (from CD if it
matters; there is a CMD CQD-200 or -220 as the only storage controller) and
routinely getting machine check exceptions.
> Standalone backup always boots. Sometimes I get an exception the moment I
hit <enter> on a restore; sometimes in the middle of the restore, sometimes
it runs to successful completion.
> VMS never boots. Sometimes I get as far as the date prompt (I took out
the battery), sometimes it gets a little farther, frequently it's before
anything appears on the console at all.
> The exceptions booting VMS occur the same if I attach another disk with
VMS 5.5 already installed; if I replace the KA630 and M7609 with a KA655
and M7622, it all seems to run fine.
> The KA630 power-on diagnostics all pass, but... it smells like a memory
fault to me. What are the odds there could be a memory fault that isn't
caught by the diags?
> until further notice
Well, if the KA630 diagnostics are anything like the KA650 diagnostics, the
power on self test is not too thorough as I learned. I found 10 bad DRAMs
on a KA650, the POST only found 2 of them. The rest I had to test by
running tests from the monitor with tighter parameters.
You should get into the console monitor on the KA630 and see if you can get
a list of tests to be run with the TEST command. Sometimes they have
parameters, and you can specify more thorough tests to be run. Keep in
mind, they may take considerably longer to run than the POST does.
I'm speaking from KA650 experience here, but I was able to run the MEM_Data
test on all of memory with an address increment of 1. It took about 4 or 5
hours to complete I think, for 8MB of RAM.