Advice needed: Entry point into things PDP-8

[Carlos E Murillo-Sanchez]

Ethan Dicks wrote:
> 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.
-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.

> >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
>
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.