22 Oct
2018
22 Oct
'18
8:39 p.m.
Greetings all...
I have been pondering something and would love to receive feedback from
you.? The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular.? Now,? I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then.? I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
I happen to have three VT78 cpu boards (sans the RAM board) and two
vt278 cpu boards.
All were in rather sorry condition; I picked them up from a junk pile
that was stacked
several feet high and in which the contents were mostly random. Thus,
the VT78 boards'
components were scratched and in fact two of them are missing the
control panel ROM chip.
Otherwise they are complete, but I am missing the RAM boards.? The VT278
boards
were further abused by someone who yanked out the oscillators and a few
TTL chips,
damaging several traces, which I have now repaired.? Alas, only one of
them has the
HM6120 cpu chip, and I do not know if it is good or not. Both are
missing the SMC5037
CRT generator chip.? Other than that, they are complete.
So, now that we all know what I have, let me say out loud what I've been
thinking:
If I try to build actual hardware:
I've read that the VT278 has serious software compatibility issues with
older software
due to the use of the HM6121 I/O chip.? So even if I get an adequate
keyboard, buy the
CRT chip and manage to use it to drive a monitor, I would need an
original floppy drive
system and media, because I do not have the DP278 serial comms board
that would allow me
to send the VT278 a program to run;
For the VT78, I would need to hack a memory board, and, since it can be
coaxed to accept
a program to run if it is fooled into thinking that it is loading a
program from an
MR78/paper tape, perhaps I could make it boot something.? I would need
to wire-up
and arduino or something like it to translate the keyboard and display
terminal
chatter in the serial console into something usable.? But, that's three
hardware
projects (memory board, MR78-like contraption, microcontrolled serial
console
translator)...
The last hardware option is to go and make an SBC6120RBC;? I would need
to buy
programmers for the GAL/PAL devices, and I've heard that not all
programmers can deal
with the kind of chips used in it.? And, if it turns out that the HM6120
chip that I
have is bad, I would have to hunt down one of those rare beasts.. It
would be awesome, though,
to have an SBC6120RBC up and running, and be able to time actual
hardware running
FORTRAN.
And then comes the emulation option, with the PiDP-8.? I have to say
that the emulation
of the blinkenlights is very, very attractive to me, and this option is
a no-brainer
hardware-wise.
So...? am I missing something in my estimation of the effort involved in
these options?
What would _you_ do?
Carlos.
22 Oct
22 Oct
9:11 p.m.
On Mon, Oct 22, 2018 at 11:39 PM Carlos E Murillo-Sanchez via cctalk <
cctalk at classiccmp.org> wrote:
Greetings all...
I have been pondering something and would love to receive feedback from
you. The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular. Now, I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then. I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
Carlos,
My opinion....Get a PiDP8. They're great for so many things including
testing, file transfer, and making disks. I have mine set to boot into simH
via serial terminal so it will immediately act like a PDP 8 running OS/8.
Once you get a working real PDP8, whatever, the type you can use the PiDP8
safely to experiment, compare and contrast, build media, etc
I have documented the process on my web site, and there are many others who
have also done this.
Bill
9:17 p.m.
Hi Carlos,
With the cost of PDP-8 parts and the need for maintenance and repair, if
you can find an emulator that will do what you want, go for it.
Paul
On Mon, Oct 22, 2018 at 10:39 PM Carlos E Murillo-Sanchez via cctalk <
cctalk at classiccmp.org> wrote:
Greetings all...
I have been pondering something and would love to receive feedback from
you. The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular. Now, I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then. I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
I happen to have three VT78 cpu boards (sans the RAM board) and two
vt278 cpu boards.
All were in rather sorry condition; I picked them up from a junk pile
that was stacked
several feet high and in which the contents were mostly random. Thus,
the VT78 boards'
components were scratched and in fact two of them are missing the
control panel ROM chip.
Otherwise they are complete, but I am missing the RAM boards. The VT278
boards
were further abused by someone who yanked out the oscillators and a few
TTL chips,
damaging several traces, which I have now repaired. Alas, only one of
them has the
HM6120 cpu chip, and I do not know if it is good or not. Both are
missing the SMC5037
CRT generator chip. Other than that, they are complete.
So, now that we all know what I have, let me say out loud what I've been
thinking:
If I try to build actual hardware:
I've read that the VT278 has serious software compatibility issues with
older software
due to the use of the HM6121 I/O chip. So even if I get an adequate
keyboard, buy the
CRT chip and manage to use it to drive a monitor, I would need an
original floppy drive
system and media, because I do not have the DP278 serial comms board
that would allow me
to send the VT278 a program to run;
For the VT78, I would need to hack a memory board, and, since it can be
coaxed to accept
a program to run if it is fooled into thinking that it is loading a
program from an
MR78/paper tape, perhaps I could make it boot something. I would need
to wire-up
and arduino or something like it to translate the keyboard and display
terminal
chatter in the serial console into something usable. But, that's three
hardware
projects (memory board, MR78-like contraption, microcontrolled serial
console
translator)...
The last hardware option is to go and make an SBC6120RBC; I would need
to buy
programmers for the GAL/PAL devices, and I've heard that not all
programmers can deal
with the kind of chips used in it. And, if it turns out that the HM6120
chip that I
have is bad, I would have to hunt down one of those rare beasts.. It
would be awesome, though,
to have an SBC6120RBC up and running, and be able to time actual
hardware running
FORTRAN.
And then comes the emulation option, with the PiDP-8. I have to say
that the emulation
of the blinkenlights is very, very attractive to me, and this option is
a no-brainer
hardware-wise.
So... am I missing something in my estimation of the effort involved in
these options?
What would _you_ do?
Carlos.
23 Oct
23 Oct
5:55 a.m.
There's also our Ohio Scientific 560Z "Processor Lab" reproduction:
http://www.glitchwrks.com/2017/02/26/osi-560z-build
It uses the Intersil IM6100 and executes PDP-8 code. Memory management is
implemented in handlers written in 6502 assembly on the host system, so you
can have whatever memory management you like. I believe one of the guys on
the osiweb.org forums has PDP-8/e memory management working. I don't know
if he has OS/8 running yet, but does have at least FOCAL going. You of
course need a 12-bit memory board, which we also make (uses modern
components, works with FeRAM for a core-like experience). And you'll need
some sort of host system, the simplest being an Ohio Scientific 502 at the
moment (basically a single-board 6502 system with serial console).
That's probably the cheapest/most reliable *non-emulation* route. Of
course, emulation is going to be both cheaper and more reliable.
Thanks,
Jonathan
On Tue, Oct 23, 2018 at 12:17 AM Paul Anderson via cctalk <
cctalk at classiccmp.org> wrote:
Hi Carlos,
With the cost of PDP-8 parts and the need for maintenance and repair, if
you can find an emulator that will do what you want, go for it.
Paul
On Mon, Oct 22, 2018 at 10:39 PM Carlos E Murillo-Sanchez via cctalk <
cctalk at classiccmp.org> wrote:
Greetings all...
I have been pondering something and would love to receive feedback from
you. The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular. Now, I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then. I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
I happen to have three VT78 cpu boards (sans the RAM board) and two
vt278 cpu boards.
All were in rather sorry condition; I picked them up from a junk pile
that was stacked
several feet high and in which the contents were mostly random. Thus,
the VT78 boards'
components were scratched and in fact two of them are missing the
control panel ROM chip.
Otherwise they are complete, but I am missing the RAM boards. The VT278
boards
were further abused by someone who yanked out the oscillators and a few
TTL chips,
damaging several traces, which I have now repaired. Alas, only one of
them has the
HM6120 cpu chip, and I do not know if it is good or not. Both are
missing the SMC5037
CRT generator chip. Other than that, they are complete.
So, now that we all know what I have, let me say out loud what I've been
thinking:
If I try to build actual hardware:
I've read that the VT278 has serious software compatibility issues with
older software
due to the use of the HM6121 I/O chip. So even if I get an adequate
keyboard, buy the
CRT chip and manage to use it to drive a monitor, I would need an
original floppy drive
system and media, because I do not have the DP278 serial comms board
that would allow me
to send the VT278 a program to run;
For the VT78, I would need to hack a memory board, and, since it can be
coaxed to accept
a program to run if it is fooled into thinking that it is loading a
program from an
MR78/paper tape, perhaps I could make it boot something. I would need
to wire-up
and arduino or something like it to translate the keyboard and display
terminal
chatter in the serial console into something usable. But, that's three
hardware
projects (memory board, MR78-like contraption, microcontrolled serial
console
translator)...
The last hardware option is to go and make an SBC6120RBC; I would need
to buy
programmers for the GAL/PAL devices, and I've heard that not all
programmers can deal
with the kind of chips used in it. And, if it turns out that the HM6120
chip that I
have is bad, I would have to hunt down one of those rare beasts.. It
would be awesome, though,
to have an SBC6120RBC up and running, and be able to time actual
hardware running
FORTRAN.
And then comes the emulation option, with the PiDP-8. I have to say
that the emulation
of the blinkenlights is very, very attractive to me, and this option is
a no-brainer
hardware-wise.
So... am I missing something in my estimation of the effort involved in
these options?
What would _you_ do?
Carlos.
7:52 a.m.
On Tue, Oct 23, 2018 at 8:11 AM systems_glitch via cctalk
<cctalk at classiccmp.org> wrote:
There's also our Ohio Scientific 560Z "Processor Lab" reproduction:
http://www.glitchwrks.com/2017/02/26/osi-560z-build
That's fun.
For a long time now, I've wanted to noodle around on a Challenger 3.
We had a family friend in the 1970s who had one and I used to go visit
and spend hours on it. I was using PETs every week at the same time
so it was a bit of a shift to a floppy-based system and one that had 3
CPUs on top of that! I started fiddling with PDP-8s about 4-5 years
later and was surprised to learn there was a PDP-8-on-a-chip (IM6100
then later then IM6120). Very cool that you've made it available
now. I just don't think I'll ever run across a Challenger 3. I
haven't in the past 30 years, and I live about 2 hours from where they
were made.
Was the original 560Z a popular board? I'm guessing it was a niche product.
-ethan
8:40 a.m.
On Mon, Oct 22, 2018 at 10:39 PM Carlos E Murillo-Sanchez via cctalk
<cctalk at classiccmp.org> wrote:
you. The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular. Now, I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then. I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
I would probably do all the things but in a particular order.
If my goal was to learn PDP-8 software, I would just start with simh
running on anything. I have a PiDP-8. It's nice. You definitely get
the feel of running an older PDP-8 (except no noise for floppy drives
or DECtape, and no seek time) but under the blinky covers, it's
running simh. You can learn everything about the configuration of
PDP-8 models, about memory, and all the programming languages with
simh. From there, consider a PiDP-8 if you want a quick junior-sized
emulated machine for the look and feel of things.
The SBC6120 with FB6120 is also nice. I have one. Unlike the PiDP-8,
the SBC6120 has a native 12-bit microprocessor (IM6120) and isn't
emulating anything except running some front panel ROM code to handle
disks in a way that hides the details from the OS/8 side of things
(much like the DECmates do). Unfortunately, they are expensive. Not
many were made and they weren't exactly cheap when new. As for the
GAL programmer, the GALs in the SBC6120 are rather ordinary but, yes,
some programmers can't handle them. I have multiple device
programmers and even the one from 1990 can program 20 and 24-pin GALs
(I'm not sure about newer programmers - I don't have one because my
older ones work fine). Someone on the list could probably bang them
out for you for a few dollars unless you really wanted to own the
entire hardware toolchain.
From there, one of the challenges of repairing your
VT78 and VT278
boards is there's no blinkenlights console to assess repair
status
during the repair or to try to toggle in test programs. Replacing a
ROM is easy enough, even if you have to make a pin-swapping socket
adapter to use a modern EPROM (I don't know what type of ROM is in the
VT78, but it's possible that it's something standard like a 2708 or
2716).
Getting replacement parts for your VT278 is probably not all _that_
hard - one likely source is a DECmate II or III board, if you can find
a spare. Last time I bought one, it was about $50 but it probably has
gone up a little.
The VT278 does have a compatibility issue with the console SLU (03/04)
and the flags. That's why there's OS/278 in the DECUS collection. If
you were going to write your own code from scratch, you'd have to take
the operation of the console device into account when writing your TTY
code, and you might not be able to just run anything you find. I have
a VT278 but have only run WPS-8 on it, not OS/278 so I can't provide
deep details. You would likely want an RX02 (and cable) if you were
going to resurrect the VT278. The cable can be made (DB25 one end,
DC37 other end, and the pinouts are available). Inside the VT278
pedestal is a _real_ RX02 but there's a simple 40-pin-to-DB-25 passive
board inside the case, much like the one in an RX02 for a MINC-11,
and, again, this can be made new. Finding any RX02 drive is an
exercise in shopping and paying freight, but then you'll need someone
to at least cut some starter floppies for you.
So if you are going to go the emulation route, I'd start with just
downloading simh and some OS/8 image files (RK05 or RX02) and learning
the software side of things. This may generate enough interest to
want to explore the hardware side of things, and for that, you
definitely have a swath of projects in front of you with varying
degrees of cost and effort.
-ethan
24 Oct
24 Oct
7:49 p.m.
Ethan Dicks wrote:
The control panel ROM in the vt78 is proprietary (12bit data width), so
it would have to be replaced by a more complex circuit.? But one of the
three vt78s that I have does have that chip, so this is an issue only if
I try to restore the other two boards.
Carlos.
On Mon, Oct 22, 2018 at 10:39 PM Carlos E
Murillo-Sanchez via cctalk
<cctalk at classiccmp.org> wrote:
-snip-
Based on the answers from everyone (Thanks!), I think that I will grab
one of the RaspberryPi's laying around and start using the PiDP-8
software or plain simH while I can procure the hardware side of PiDP-8;
I think that I'll perform the serial console hack on the Pi.? I will
continue to research options for programming the GALs in the SBC6120 or
SBC6120RBC, since I have one HD6120 chip and it would be a waste not to
use it.? The OSI Processor Lab route seems interesting, especially since
I have three HM6100 chips, but I think that it isn't in a stage that
allows reproducing the PDP-8 usage experience.
If you guys can recommend a cheap programmer that handles the
ATF22V10CQZ-20PU and ATF16V8BQL-15PU (SBC6120) without problems, I am
all ears.
you. The thing
is, I would like to have something pdp8-ish that would allow me to play
a little bit
with the programming languages that were available for these machines,
FORTRAN 4K and
FORTRAN IV in particular. Now, I would love to be able to time some
FORTRAN jobs just
to get an idea about what it was like back then. I am aware of PiDP-8,
simh, as well as
SBC6120, SBC6120RBC.
I would probably do all the things but in a particular
order.
If my goal was to learn PDP-8 software, I would just start with simh
running on anything. I have a PiDP-8. It's nice. You definitely get
the feel of running an older PDP-8 (except no noise for floppy drives
or DECtape, and no seek time) but under the blinky covers, it's
running simh. You can learn everything about the configuration of
PDP-8 models, about memory, and all the programming languages with
simh. From there, consider a PiDP-8 if you want a quick junior-sized
emulated machine for the look and feel of things.
The SBC6120 with FB6120 is also nice. I have one. From there, one
of the challenges of repairing your VT78 and VT278
boards is there's no
blinkenlights console to assess repair status
during the repair or to try to toggle in test programs. Replacing a
ROM is easy enough, even if you have to make a pin-swapping socket
adapter to use a modern EPROM (I don't know what type of ROM is in the
VT78, but it's possible that it's something standard like a 2708 or
2716).
-ethan
2249
days inactive
2251
days old
6 comments
5 participants
participants (5)
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billdegnan＠gmail.com -
ce.murillosanchez＠gmail.com -
ethan.dicks＠gmail.com -
systems.glitch＠gmail.com -
useddec＠gmail.com