IBM 1620 Simulation

Ray Jewhurst raywjewhurst at
Thu Aug 26 21:07:56 CDT 2021

On Thu, Aug 26, 2021 at 9:46 PM Chuck Guzis via cctalk <
cctalk at> wrote:

> On 8/26/21 5:14 PM, Ray Jewhurst via cctalk wrote:
> > Hello all,
> > Long time lurker, extremely rare poster, I was reading the Wikipedia
> > article on the IBM 1620 and became quite intrigued.  I know that there
> is a
> > simulator for it on SimH but I have never ran or simulated any
> card-driven
> > machines before.  I have all the documentation and the file
> > from bitsavers but I am not sure what to do next.  I know I would like to
> > try Monitor, Fortran-II and possibly GOTRAN but I have so many questions.
> > I read the SimH documentation which gave me some understanding but I
> don't
> > know exactly how the card decks work, how to install Monitor or how to
> boot
> > Monitor once it is installed since I know you have to boot off a deck.
> My
> > final question is, is there an easy to use card-driven machine to cut my
> > teeth on?  Also, any anecdotes on any of the old IBM computers would be
> > both welcome and greatly appreciated.
> >
> Cards are just ASCII lines separated by newlines>
> For more information, see:

 I have already read that document. The thing that stuck with me most was
the fact that you can not boot off the hard drive (or were they already
calling them DASDs?)

> It's been years since I used the SIMH 1620 simulator, so I can't even
> claim to be remotely current.  I used it to check out some sample code
> back then.
> My reaction:  It's just not the same.  I guess you had to be there.
> Did anyone manage to snag a copy of Monitor IID?  Or is the only extant
> version Monitor I?   The differences were significant.

 I only saw Monitor I. Will it even run on a 1620-II?

> Also, don't forget SPS!
 SPS is included both standalone and in the Monitor I distro, so is

> If you're new to the 1620, I recommend the following book:

Thank you. I will check it out starting tonight.

> If you want to use a totally (i.e. no disk) card-driven version of the
> 1620, I'd recommend that you start with simple machine language
> programs.   I (dimly) recall that using the card-only FORTRAN compiler
> was a bit of a chore:  read pass 1, read your program, while punching an
> intermediate deck, read pass 2 and the intermediate deck, read the
> subroutine library and wind up with an executable deck.
I will try the card-driven version first I think as an intro to cards.

> --Chuck

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