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, means 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. Sadly on CDC Hawk and CDC Lark disk packs.

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