[cctalk] Re: Intel 4004

There is little surviving software for the 4004. There are a few places with snippets of code to do things like add or subtract several digits but my searches of the internet have shown little actual code. The NBS has some code to track satellites and correct for time delays from their clocks ( think GPS ). I'd had a spare 4004 and always wanted to do something with it. I found that the library for work done at the Navy Post Graduate School in Monterey California had 2 projects that students of Gary Kildall created. One was a load calculator for helicopters and the other was for calculating closest point of approach for ships. I'd been unsuccessful at down loading the helicopter code but was able to down load the ships document. I'd let the listing sit for 10's of years while always on the back burner. Over the years I'd acquired the needed parts. I did make a few substitutions, though. The original used 13 each 1702A EPROMs. Since that exceed my budget for a PC board space, I chose the option of using a 4289 and a 2732 EPROM. I did use the original designs number of 4002s, as using RAM through the 4289 would have made significant changes to the software. The problem of the circuit needed to be dealt with. The document had a page labelled 'schematic' that turned out to be the keyboard layout and display layout( both of which I ignored and used my own layout that I though was better ). Before getting to the board design, I needed to get working software. The listing was done on a ASR33 with a deeply rutted platen, typical of hand-me-down things used by a school's command. Letters like R or P would look like F and 0 would look like C. Other letters were easy to figure out but still often had their right edge missing. After entering the list by hand, I'd feed it into my assembler and the tried to run it with my simulator. I'd make corrections as I got the code running. I need to create the circuitry for the keyboard decoder, that took 25 buttons to the 4 bit data bus input of the 4004. There was enough description in the document to create the LED display but I did missed one thing ( that I'll mention later ). I created the board with my typical incorrect wiring, requiring several extra cuts and jumpers. ( the concept was right but I got the pins of the 7402 mixed up.) The one thing that I'd missed was the order of the digit scan. I assumed left to right but the code was actually right to left. After so many cuts and jumpers to get the keyboard right, I dreaded more to fix the scan order so I made the one change to the original software to do right to left ( I still feel bad about that change ). I thought I'd talk a little about how a Closest Point of Approach Calculation is done. Normally it had been done by a graphical method of line drawing on what is called a plotting maneuver board. One used graphical calculations for the trig used. It was all done by pencil and parallel. It is so important that, I believe, that to this day a ship's pilot still needs to be able to do this calculation on a maneuver board, even though such graphical displays are capable of doing such, today. Large ships require significant knowledge of where they are relative to other fixed and moving objects in order to determine the safest path to proceed. A broken display is not time to learn how to do such a calculation. This 4004 calculator used a newly found way of doing tangent calculations, called the CORDIC method. One could clearly see the influence of Gary Kildall's hand in this code. It is noted that he wrote the division routine used and the organization of the code clearly shows the influence of a seasoned programmer. Bring such code back to life was almost as much as making a 4004 processor from discrete transistors but I felt was for me as part of my bucket list. Things I needed to do, included writing an assembler, writing a simulator, learn a PC board CAD, transcribing a poor quality listing, debugging the poorly transcribed listing, creating the keyboard decoder and instrumenting my simulator to be the calculator. Dwight ________________________________ From: ED SHARPE via cctalk <cctalk(a)classiccmp.org> Sent: Tuesday, November 21, 2023 1:03 AM To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org> Cc: ED SHARPE <couryhouse(a)aol.com> Subject: [cctalk] Re: Intel 4004 So what are the other contenders and what do they bring to table Sent from AOL on Android On Mon, Nov 20, 2023 at 9:06 PM, Adrian Stoness via cctalk<cctalk(a)classiccmp.org> wrote: someone should build it in minecrsft On Mon, Nov 20, 2023 at 7:01 PM ben via cctalk <cctalk(a)classiccmp.org> wrote: