Goals

eM18 - The Molecular 18 Emulator

Not having a working M18 is a rotten shame, and not getting my act together in the late 1990s I didn't hover a few machines up! We do have a Mk V and a Distributor at the museum, and I am hopeful we might get one working. We do have the OS and Application disks thankfully.

So, in the mean time let's write an emulator. (There is a rich history of writing emulators for historic machines - simh being the most famous).

eM18 is written in simple plain C code. I am not sure what it will run on finally, but it runs well on my development machine and on a tiny (and cheap) Raspberry Pi.

On starting the emulator:

Molecular 18 Emulator

Building processor, 32k core memory, DD1600 disk drive as Unit 70
Loading core image
Core image read from /home/steve/Documents/mollyimages/coreImage.txt
Loading default disk images
70 Fixed master27
70 removeable security26
Creating terminals and printers
Adding Terminal - /dev/ttyUSB0 - device 50/40
... connected
>

In the settings file, we specify 32K Words of core and a DD1600 drive with two surfaces at dev 70.
Again in the settings file, device 50/50 is mapped to a serial port.

This is the help screen:

Core:

dc nnn        Display core from nnnnnn or nn/nnnn
fc nnn        Dump one page to host disk from nnnnnn or nn/nnnn
ac nnn        Amend from nnnnnn or nn/nnnn
cc            Clear - no warnings
sc ad sc      Save core from ad (address) to sc (sector)
lc ad sc      Load core from sc (sector) to ad (address)

Disk:

ds nnn        Display sector nnn
fs nnn        Load/Amend sector
cs nnn        Clear sector nnn
ssec          Security Copy

Run:
dp            Display processor state
s             Display processor stats
run nnn       Run from PC = nnnnnn or nn/nnnn
b nnn         Set breakpoint at nnnnnn or nn/nnnn
step nnn      SingleStep from PC=nnnnnn or nn/nnnn
b             Boot LOS
sop           Boot Special OP
st            Boot single task

t xxx Trace On from nnn or nn/nnnn
. Quit