History of Computing Collection

RCA COSMAC Development Kit

If you peruse the Wikipedia article for the RCA 1802 processor, there's a very short mention of the Microboard development system:

The "RCA Microboard" text here is a dead link, with no target. Even a search directly for the Microboard and related hardware shows very little result, with no substantial detail.
This article, therefore, will serve as the source of detail for those interested in both the RCA Microboard systems, and the RCA COSMAC Development System (CDS).

 
Origin

Our RCA equipment is part of the John Ceres Amson Collection, the equipment being shown here was used by a company called Positron, based in St Andrews, Scotland, and was used to create the first civilian tide-predicting software.
John Ceres Amson's obituary …
Positron …
Signs of MS-DOS …
Encryption devices …

 
The Platform

 
The RCA 1802 is a commercialization of a TTL computer designed by a man called Joseph Weisbecker (of CHIP-8 fame), courtesy of the diverse projects running at RCA Laboratories. It's the first processor family based on the CMOS technology - with a couple notable built-in advantages over MOS and NMOS processors that must perform some variation of constantly refreshing the data stored within registers and thus cannot stop the processor core and halt execution for any non-trivial amount of time. The static core of the 1802, on the other hand, can be paused indefinitely, run arbitrarily slowly, or run one cycle at a time.

Apart from the CMOS core, it had several variants, among them being a radiation-hardened version designed for use in space (where there is no atmosphere to provide protection against high-energy particles or solar radiation) - used in various satellites and probes, such as the Gallileo probe and the Hubble Space Telescope - and a version of the processor with built-in ROM, RAM and timer: a self-contained computer, akin to a System-on-Chip.

There are also variants of the 1802 such as 1805 and 1807, which add extra instructions and capabilities.
But all of this is detail that you can get from the Wikipedia article, so let's move onto something you can't just find on the Wiki:

 
Microboard

The Microboard system is, to put it as simply as possible, a supported platform onto which you can build completely customized computers using a standard form factor case containing a standard backplane connector format.

That essentially means that the Microboard itself is a small case with a small circuit board containing multiple sockets, and a lot of documentation telling you how to build PCBs that insert into those sockets to connect to each other, allowing for separation of purpose; a CPU & I/O card, a ROM/RAM card, a peripherals card, etc.

There are pre-designed cards available for purchase from RCA, allowing you to build a computer from their designs. One of the valid designs is of an RCA ELF computer - the first home microcomputer designed from the 1802 processor. It saves and loads programs from cassette, and is surprisingly capable for the simplicity of the device itself.

Our Elvish Microboard system looks like this:

We have a second Microboard, which has been modified heavily by its previous owner:
Whose purpose is…

The Microboards we have came with the following cassette players:

And the following accessories and cards:

COSMAC Development Kit

There are two variants of the CDS, the CDS 1 and CDS 2. We have a couple of things from the CDS 2 but not the full kit, and parts of the CDS 1 kit. These are not marked as being delivered on the original receipts, therefore we suspect that Amson was given a prototype / early CDS 2 kit, before the public release of the equipment.

The CDS itself is an expanded version of the Microboard system, with a similar concept: a backplane allows for connecting the system bus between a large number of cards, and each may deal with any aspect of the system the designer wishes them to.

Certain ports are best used for certain things, as not all bus lanes are attached to every socket, but the documentation explains which.

The CDS has two major differences to the Microboard system: instead of programs stored on cassette, they are stored with a dual 8" floppy disk drive (yes, eight inch!):

The second difference is that the CDS has a Data Terminal present by default, allowing for direct textual manipulation of the processor and the program running inside it.

The CDS itself also provides some controls of the processor: it can show the current state of the address and data lanes, and can pause and single-step the processor's clock using switches on the front case.

 
Micromonitor

The Micromonitors (nicknamed in our Collection as "Data Cases") are RCA's approach to portable debugging of the 1802 system. It can, in a nutshell, intercept the processor's control signals and act as a man-in-the-middle for any system encountering program errors. The 1802 processor is moved to the socket inside the Micromonitor, the Micromonitor is connected in the place of the original processor, and a terminal is optionally connected to the Micromonitor.

In this configuration, the keypad on the Micromonitor allows for sending signals and commands directly to the processor, for changing the state of registers and memory, for stepping and stopping the processor, for manually running instructions.

It fully utilises the advantages of the static core of the COSMAC processor, and allows for a significant step-up in programmer friendliness of software written with the system.

We have two Micromonitors, which also came with a portable input device:

Along with these, there was also a large scale data analyzer, presumably for connecting to the other lanes of the system bus.