[ih] Intel 4004 vs the IMP

[Jack Haverty]

On 11/15/21 8:00 AM, Clem Cole via Internet-history wrote:
> But having looked at some of the IMP code that has
> leaked out,
  I wouldn't say "leaked out".    It was methodically resurrected and 
Dave Walden (who was one of the programmers) has put it on his 
website.   There is quite a lot of information about the IMP code, 
including several complete listings of its program, in 316 assembler of 
course, and its recent resurrection, available at:

https://walden-family.com/impcode/

I'm not sure where it is now, but the code itself also exists in 
runnable form and has been successfully run, using a Honeywell 316 
emulator, to recreate the original 4-node early ARPANET configuration.   
It's ready for someone to resurrect one of those early host computers to 
create traffic.

I had the opportunity to dive pretty deeply into the code itself while 
working on a patent dispute about ten years ago, and figure out exactly 
how it did what we remember it could do.   It's a fascinating and 
impressive piece of work.   The IMP software probably violated lots of 
principles of modern programming practice, e.g., using techniques like 
self-modifying code.   But it worked. You did what you had to do with 
the hardware that was available.

Anyone who has the interest, curiosity, and time to look at a historic 
chunk of actual code, I suggest looking at that IMP code. It really 
should be in a museum.

/Jack Haverty