There is a bug in the TTY CLI, it accepts characters as ‘;’ and ‘:’ as valid hex and translates to A..F.

KIM
0200 A9 ;;
00BB 00 ::
00AA 00 ????
FFFF 1C

More about this innocent feature here: PRTBYT, GETBYT and PACK

On this location you can find the open hardware source of a RAM card made for the MTU bus

he RAMpager is a MTU banked RAM expansion for the KIM-1: the board supports up to 1MB (that’s three orders of magnitude above more than the original 1152 bytes!) of memory and maps it to a 4KB window placed between 2000h and FFFFh. The window can be mapped to different banks for read and write operations via two control ports.

It supports an optional internal/external backup battery to keep the data in the SRAMs valid across power cycles.

On these pages I will try to explain how all this is working together. It will not be a rewrite of the KIM-1 user manual, read that first, but more a deeper personal dive into the software and hardware of what the makes the KIM-1 tick. It also expects a basic knowledge of the 6502 and digital electronics.

Based upon my experience and study of the KIM-1 since 1979. The first years to learn the 6502 CPU and the 6530 RRIOTs. The next time when I wrote the KIM-1 Simulator (2015 to now). Many notes on paper and files everywhere. Now consolidated in a lot of pages.

Work in Progress July 6-13, 2026

Problems with the KIM-1 TTY character input

1. The KIM-1 hardware is hardware echoing incoming serial characters to the output, no echo in software involved, so you cannot influence what appears on screen. Very annoying!
2. The KIM-1 GETCH routine is blocking, no way to check for a character coming in, like a Break. waiting.
   Also quite annoying if porting other software to the KIM-1 or you want the program interruptable.
3. While a program is running something CPU intensive and you type something the program is not really waiting for, the characters appear on screen. Because the KIM-1 does hardware echoing of TTY input, this is unavoidable it seems

Here I present solutions for these problems in software, made possible by the genius hardware design of the KIM-1 TTY I/O.
You can have serial input wihout echo, non-blocking and even make the TTY input deaf for unwanted input.

Are they perfect? Maybe not, it is still bitbanging the incoming serial signal. It can miss the correct starting point for the incoming character bit stream.
If you want a perfect solution, you will need interrupt driven ringbuffered serial I/O with a dedicated IC like the 6850, 6511 etc.
Without this extra hardware you can achieve acceptable results with these routines.

Settings 2.3.1

So in June 2026 I have typed in the source of the KIM-1 monitor as it is listed in the User manual. Every line has the same line number, all text including comments is as in the paper listing. The listing is also paged as the original. Converted to a modern MOS Technology assembler format (I used TAS32), that delivers the exact ROM binary (including those 00 filler bytes!) as dumped from the real 6530-002 and -003 by me.

KIM-1 Monitor source, listing and binaries and TASM32 archive

More on the KIM-1 ROMs here.

It’s written in 6502 assembly using DASM assembler and MAME as developing tools.

You can download it here

How to play

The game follows the basic rules of mastermind: the codemaster generates a hidden code and you have to guess it in a limited number of tries, while the codemaster gives you a report on how much you got right for each guess.

The codes are be composed by 4 symbols, each symbol can be one of the following 8 characters: `A`, `B`, `C`, `D`, `E`, `F`, `G`, `H`. Note that a character appearing multiple times in a code is perfectly valid.

After you type in the 4 character code and press `RETURN`, the codemaster will analyze your guess and report the result using 4 symbols:

– `O` indicates that one symbol is both the right character and at the correct spot
– `*` indicates that a symbol is a character that appears in the code, but is in the wrong place
– `.` Indicates that a character is not present at all in the code

Note that these are **NON POSITIONAL**, and they’re just shown in order of precedence: first `O`, then `*`, then `.`. They bear no information on which of the characters is right. You’ll have to find that yourself.

In case you want to cancel a guess before submitting it (to avoid wasting a try), you can press `BACKSPACE`. The guess submission will be aborted, no analysis will be performed and you’ll be able to submit a new guess.

Does it run on the KIM-1 Simulator? YES!

You only have to set the FOCAL_V3D break setting in the Settings.

I ordered one and indeed a 40 pin IC appeared. So this is not a 6503!
Then I searched the internet for the 338-6503 printed on the IC and found references to it being a R65C02.
And indeed, the 6502 testers recognized it as working 65C02. Weird!
The ‘6503’ was found in Apple IIe and Apple IIc computers.

Rockwell R6500/1 family

The R6500/1 is a 6502 , ROM (2K) 64 bytes RAM ,4×8 bit I/O, a 16 bit timer with I/O pin.
The ROM contents are factory mask-programmed, not programmable by the user.

This makes it a standalone microcomputer, no extra RAM/ROM or decode logic required.

There are no external address lines or data lines, the 6502 is all internal except the interrupt lines and clock.

Rockwell R6500/1EC

To develop applications with the R6500/1 Rockwell developed the R6500/1EC. This IC has the same pins as the R6500/1 but adds address and data lines and relies on an external ROM.

Downloads

	R6500/1 One-Chip Microcomputer
	R6500/1E Microprocessor Emulator Device
	R6500/1 Microprocessor Programming Reference Card

The 6500/1 has been used for example in the AMIGA 1520 Plotter. I found this image on ebay: