Writing emulators [Was: Re: VCF PNW 2018: Pictures!]

[Pontus Pihlgren]

On Mon, Feb 19, 2018 at 06:36:13PM -0600, Adrian Stoness via cctalk wrote:
> whats invovled in makin an emulator?
> i have a chunk of stuff for the phillips p1000

I would say it depends a lot on how complex your target machine is. But 
in essense you will have to write code for each device you wish to 
emulate mapping their functionality over to your host machine, the one 
running the emulator.

As a minimum you will write code for the CPU and some sort of output 
device, such as a serial console. For some machines you might need 
images of ROM code in order to be fully compatible with existing 
software.

I wrote a PDP-8 emulator for fun. The basic CPU and serial was done in a 
few hours. I then hardcoded the paper tape loader in memory and allowed 
input to be read from an image file.

Adding extended memory support and running conformance tests has taken 
the bulk of the time.

/P