6530 replacement board

Christer from Sweden built an Eduardo Casino designed KIM-1 replica. And as we know, the 6530 replacement is an issue.
Not only for replica’s also for broken original KIM-1s.

So he designed his own, more compact original looking adapter.
He created this adapter because he wanted something that would work and look a little more unobtrusive than the other adapter boards that are available but still look somewhat genuine (no FPGA). The design is inspired by the Corsham 6530 replacement board but made way smaller by using SMD components and stacking the 6532 on top of the adapter board.

A newer design promised to be much more compact.

Circuit Diagram Poster, KIM Hints, First Book of KIM

While suffering from a bad cold I tried to entertain myself with essential KIM-1 documentation that needed version information and a good cleanup of the scans.

Circuit Diagrams, the big poster. Every KIM-1 came with one. I have several of them. As far as I can see the contents stayed the same trough the years. What did change was the paper it was printed on, from heavy carton to flimsy paper. And the 1977 version had different background colors, blueish.

There was some version information on the posters. 1975, 1976 3.2 m 11-76, 1976 4m3-76, 1977 5m 1-77. And the Rockwell branded one of course had the Rockwell imprint.

All can be seen on the new KIM-1 circuit Poster page, with high quality scans also.

KIM Hints, I have two versions, one with a greyish cover, the other pure black and white. Contents seem identical. An essential companion to the KIM-1 User manual.
Newly scanned in high quality here.

Every KIM-1 user had to have the First Book of KIM. Written by Jim Butterfield, Stan Ockers and Eric Rehnke (and many other authors!), first published 1977.
Invaluable source of information on programming the standard KIM-1. Background, games, utilities such as Hypertape.
Many reprints, many publishers.
The scan I had was done very bad, and that was the only scan ever made it seems. That had to be improved upon, it is such an essential book for the KIM-1..
Two versions are now scanned in high quality, the 1977 edition and the 1977,1978 edition (Hayden Book Company). In the later version many errors were corrected.

KIM KIM-1 which is what?

MOS Technology started development of the 6530 RRIOT very early after/during the 6501/2 development. All in 1975.

The first version of the Hardware Manual has this mention of KIM and TIM:

The KIM and TIM were mentioned as Keyboard and Teletype Input Monitor, indicating these are the 6530-002 and 6530-004 RRIOT IC’s. Indeed these ICs were sold later on.

The KIM-1 computer was developed later, with the KIM RRIOT and the 6530-003 audio cassette interfacing ROM using the KIM 6530-002 RAM and I/O ports.
The KIM-1 was not called -1 as first version, but for the 1K RAM included on the computer.
First shipping of the KIM-1 started in early 1976, then the first articles in the magazines and advertisements appeared.

So KIM is the 6530-002 RRIOT IC, KIM-1 is the computer around the KIM and 6530-003.

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KIM-1 Circuit poster

With every KIM-1 came a large poster with the Circuit Diagram. The circuit stayed the same from 1975 to 1977, but there were version numbers in the lower right corner. See below for what I have as Circuit poster versions.

First I show you the high quality scans of the Circuit Diagram.

KIM-1 circuit diagram
Rockwell branded circuit diagram
KIM-1 poster in high resolution, large picture!
KIM-1 poster in high resolution,
cleaned up by Joshy of Forum64 and me (August 2022)
KIM-1 poster in high resolution, cleaned up and with wide borders
KIM-1 poster in high resolution, scan by Dave McMurtrie
Redrawn KIM-1 circuit diagram, Ruud Baltissen
Redrawn KIM-1 circuit diagram

Circuit Diagram versions
The size stayed the same, it came as a folded poster. Some on sturdy carton, some on thinner paper. The circuit stayed the same but there were different years and small (version) strings on the right bottom.

Only the 1977 and the Rockwell versions introduced a change: the colors were changed into all blueish.

Here a list of what I have on Circuit Diagrams:

1975
1975
1976 3.2 m 11-76
1976 3.2m 11-76
1976 4m3-76
1977 5m 1-77
1975 Rockwell

2K Symbolic Assembler for the KIM-1

The 2K Symbolic Assembler, by Robert Ford Denison. An assembler and editor in 2K!

This small program allows to assemble a program up to 1K on a KIM-1 system with only 4K, including 2K for the assembler.
One can enter program in the built-in line editor and assemble to memory.

Published as a small book by Robert Ford Denison around 1980, a scientist who is now Adjunct Professor Ecology, Evolution, and Behavior, College of Biological Sciences.
In the book the program is described in detail and in source format, a binary dump is added.
Two versions for the KIM-1 (at location 0200 and at 2000) and a SYM-1 version. And with the aid of Jeff Tranter available in source and binary format for KIM-1, SYM-1 and the Apple 1 Replica.

A quality improved version of the book added to the Software pages.

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A 2K Symbolic Assembler for the KIM-1

A 2K Symbolic Assembler, by Robert Ford Denison. An assembler and editor in 2K!

This small program allows to assemble a program up to 1K on a KIM-1 system with only 4K, including 2K for the assembler.
One can enter program in the built-in line editor and assemble to memory.

Published as a small book by Robert Ford Denison around 1980, a scientist who is now Adjunct Professor Ecology, Evolution, and Behavior, College of Biological Sciences.
In the book the program is described in detail and in source format, a binary dump is added.
Two versions for the KIM-1 (at location 0200 and at 2000) and a SYM-1 version

Jeff Tranter converted the source and the dump in the book to CC65 (CA65) source format in 2012 for KIM-1 and SYM-1, with a version for the Apple 1 Replica.
You can find his work here (or in the download below)

I rescanned the book in higher quality in October 2025 and tested the program in the KIM-1 Simulator as you can see in the screendumps above. I managed to edit and assemble a three line program! The user interface requires careful reading of the book, it takes some time to understand. Do not press TAB as I did in my test, just the SPACE key!

2K Symbolic Assembler for KIM-1

2K Symbolic Assembler Sources and binaries.zip

KIM-1 replica KIM-1000 with CHIPz modules, 6530 reDIP

Mark J Koch (https://github.com/CircuitMonkey/mos-kim1-replica, ‪@markjkoch.bsky.social) is designing a not so common KIM-1 replica, the KIM-1000,
with building blocks he calls ‬CHIPz modules.

He posted photos of his first versions, it is at this moment (October 2025) a work in progress.


As you can see on the photos the CHIPz modules on a ‘motherboard’ are recognizable KIM-1 blocks:
– application and expansion connector on motherboard, with ‘bus watchers’.
– keyboard and display, all KIM-1 keys, SST switch and the six LED displays. Standard KIM-1- (a 7442 instead of a 74145).
– CPU with 65C816, not the 65C02 one would expect here.
– Control logic, with clock, Reset and NMI, memory decode K0-K7, some glue logic for RAM R/W etc. Missing is the usual TTY and audio cassette glue logic. So no serial terminal!
– SRAM module 32K, mapped to all lower address except the KIM-1 holes 1400-1FFF
– 6530-002 and 6530-003 reDIPs

reDIP 6530

One of the building blocks will be the 6530/6532 redIP. More information on that 6530 replacement here.


The reDIP RIOT is an open source FPGA board which combines the following in a DIP-40 size package:

-Lattice iCE40UP5K FPGA
-1Mbit FLASH
-5V tolerant I/O
-The reDIP RIOT provides an open source hardware platform for 6530 RRIOT / MOS 6532 RIOT replacements.

All FPGA header I/O is 5V tolerant, and can drive 5V TTL.

A Diagnostic Board for the KIM-1

It all started on the VCFED forum many years ago, where people were looking for help on repairing their KIM-1 computer.
A dead KIM-1 is no easy to troubleshoot, most ICs are not in IC sockets, so poking around with a scope is looking for dead signal lines is all you can do.
But if the 6502 is working, programs could be written to test parts.

So Dwight Elvey designed and programmed a diagnostic board for the KIM-1, to determine what might be wrong with this KIM-1.
The board switches off the 6530 ROMs and one can run tests on the onboard ROM, looking for for defective RAM, defective LED display, defective 6530 ports.

Here I present the complete design of the board, with help and permission of Dwight Elvey, Santo Nucifora and Liu Ganning.
In October 2025 I have revised the page, build a diagnostic board myself and added the reverse engineered sources of the tests in MOS Technology standard assembler syntax instead of the obscure Forth like assembler Dwight uses. The EPROM can now be build and modified with modern tools.

The board has been used by many with success. The usual suspect, the 6530-002 RRIOT, was not always the problem maker. Defective RAM IC, a TTL IC with dead ports and such also were found
by using the test programs to pinpoint the area to check.

KIM-1 Revisions, what changed?

I know of seven KIM-1 revisions, labeled Rev A-G and the first one unlabeled. Rev C is unknown!

What changed between these revisions?

Not much. The PCB underwent several changes around the logo area, from KIM-1 MOS to Commodore C-MOS. That happened from Rev A to Rev D, indicating the takeover by Commodore of MOS Technology. And some small numbers/artefacts etched in various Revs.

Some have serial numbers, the first ones on the back on the right, later had stamped/written numbers like PAxxx (Palo Alto) and SCxxx (Santa Clara) of Commodore production facilities

There was a real change in the PCB from Rev A to B.

Rev A

Rev B

The User Manual went from version 15 (January 1976) to 15A (March 1976) to 15B (August 1976) without significant changes, mostly typing errors and the change of keyboard from Rev B to Rev D.
The keyboard changed from rev B to Rev D. The SST switch moved to the other side, the first Rev keyboards were not very reliable.

Rev B

Rev D

What did not change?

The 6530 – 002 and -003 were from many different dates between 1976 and 1980. The functionality stayed the same, no software changes are known. It seems the same mask was used to produce another batch due to the demand for KIM-1s. On Rev F and G I have seen older 6530s (ceramic ones) from much earlies dates, old stock being used?

The large Circuit Diagram poster stayed the same for all revisions.

Parts used

The parts used in all these revisions changed from as much as possible made by MOS Technology (6102) to industry standard compatible types (2102). E.g the RAM ICs were all third party in later revisions.
The capacitors, mostly yellow tube types, also came in various colors and sources between revisions.

Except for Rev G no IC sockets were used.

KIM-1, were IC sockets used?

Before I saw the last revision, Rev G, I had never seen an original KIM-1 with IC sockets. All ICs were soldered right into the PCB.

Now I have a KIM-1 Rev G and a photo by Dick Dral of his KIM-1 Rev G with white IC sockets.


So the last iteration of the KIM-1 did have IC sockets.

Not only did Rev G come with sockets, they used not only white sockets, black ones too (Thanks Santo Nucifora).