Fig.2. The HRRG Terminal (Readers of a certain vintage will recall the Sperry Uniscope was a class of computer terminals from the 1960s).
a full-up mixed-technology 4-bit HRRG will be a costly and
time-consuming task.
Thus, in addition to the physical realisation, we are also
creating a virtual version of the machine – called the HRRG
Emulator. This is the part that Joe is currently working on
(Fig.1). The virtual printer shows the system being reset,
a test program being loaded from tape, and then the audit
trail of the test program being single-stepped (you can vary
the level of information being printed or switch it off com-
pletely as required).
The emulator is presented in the form of a three-shelf rack.
Each shelf contains a number of modules. In the upper shelf,
from left to right, we see the main power control module,
the system clock module, and the main CPU module. On
the left-hand side of the middle shelf we see the Program-
mers Console, which allows you to enter programs by hand
(well, mouse-click) using toggle switches and push buttons.
On the lower right-hand side, we see the virtual paper-tape
reader, which allows you to read in programs from virtual
paper tapes.
Speaking of which, Fig.2 shows the virtual HRRG Terminal
running our assembler. On the screen we see the object code
that the assembler generated for this test program. This code
was then punched to virtual paper tape, which was loaded
into the emulator.
We will be adding additional modules, including ROM and
RAM and a variety of input/output (I/O) devices, plus users
will be able to add their own devices and configure which
modules go where in the rack. Once we’ve ironed out all of
the bugs, we will be making this virtual machine available
for everyone to download and play with.
But wait, there’s more... This is where things get really
clever. Joe has architected the virtual machine to reflect the
longer-term physical implementation, including the mech-
anisms by which the various modules (cabinets in the real
world) talk to each other.
The idea is that you can start playing with the emula-
tor running on a PC, then – when you are ready – you can
commence creating one or more physical cabinets that can Fig.3. The current state of the Inamorata Prognostication Engine.