The IBM 1620¹ was a scientific computer from IBM, maybe known in the public for its use during the Gemini program. I haven't found much documentation how to actually use it, though there are some interesting application examples on bitsavers. There is at least one comprehensive example on Github.

• programs in machine code
• programs in SPS
• programs in FORTRAN

Most of these directory contain a .simh-file containing the commands for simh-i1620.

There was no readily available documentation² on how to run the assembler or fortran compiler from the digitized cards from bitsavers. My aim was to run some of the application notes from bitsavers. So let's try to understand the machine from the available documentation. The machine came with a paper tape and a card reader. The card reader interaction seems simpler (put the cards into the reader, press load) and the biggest remaining library also contained shelves with punch cards. From a user perspective, punch cards offer an easier way of patching programs than paper tape anyways. So maybe only the assembler and compilers came on paper tape.

• reading of punch cards is described on page 30³

On Bitsavers there is the innocent looking 1620.zip containing most available compilers.