COSMAC arcade, Studio prototypes

Last edited Dec 11 2018. Edited by Herb Johnson, (c) Herb Johnson, except for content written by others. Contact Herb at, an email address is on that page..


In late 2017, several old RCA Sarnoff Library's "FRED" or COSMAC cassette tapes from the mid-1970's, were digitized by the Hagley Library's Sarnoff Library collection. The digitization was a result of inquiries about a "coin-op" COSMAC machine or prototype, developed at RCA. There's considerable background information, about RCA's COSMAC development and this and other COSMAC prototypes. These circumstances were discussed in an on-line email discussion group, and privately as more people participated and as documents and WAV files became available. By 2018, both institutions became involved in digitizing their tape collections. With a final effort by Marcel van Tongreren, he converted the bulk of those audio-files into programs per computer, and emulated their execution on his EMMA 02 COSMAC emulator which now includes those binaries.

This is a story of many players, institutions, resources and methods. Some people only want the end result - a program, a hardware schematic, an emulator. But the complete story is spread among many people over time. This Web page describes the process from early efforts to final results.

Note: In following "discussion group" dialogs, there's the use of pseudonyms - it's hard to track actual names of persons, and so contact them directly. Please contact me if you the reader are aware of any errors or omissions in my personal references. Thank you. - Herb JOhnson

COSMAC, the coin-op arcade prototype, other COSMAC systems

RCA developers of the COSMAC microprocessor, worked from the early to mid-1970s to create various prototype computers,, as well as 1801 and 1802 microprocessor development systems, and later RCA video-game systems. This Web page describes discussions about and virtual restoration (simulation) of a 1975 prototype arcade-style coin operated COSMAC system, which was demonstrated briefly in an arcade. A number of technical people, personally interested in vintage gaming or the COSMAC gaming systems, worked in 2017-18 to obtain documents and audio-cassettes with binary program data, from archives of RCA prototypes and documents and tapes. Others have worked on COSMAC emulators, or documenting COSMAC systems, or displaying COSMAC and RCA artifacts.

Another Web page, COSMAC FRED cassette storage, discusses details of the analog signals on COSMAC-produced audio cassete tapes digitized by the Hagley Library, how binaries can be extracted from them, and how documentation from archives provide support for simulating and executing these dormant programs.

Another Web page, Sarnoff Collection COSMAC tapes discusses the Sarnoff Collection's process of digitizing their COSMAC tapes, and continuing efforts to decode and operate these programs and data.

RCA's prototype video games led to the Studio II video game product, the VIP and other video computing products. Here's a look at some Studio II gaming systems I've tinkered with.

By 2018 the COSMAC coin-op arcade prototype was emulated by Andy Modla and by Marcel van Tongeren on his EMMA 02 emulator.

Archives of RCA COSMAC programs and documents

If you just want "the games": Jump to the end of this Web page "COSMAC tapes processed", to see where the archives are for the COSMAC audio-cassette programs and games from the two collections of Joe Weisbecker/RCA tapes discussed on this Web page. - Herb

Here's a Web page with background on the former Sarnoff Library That facility held RCA documents and artifact, including COSMAC hardware, audio-cassette data tapes. The Library's former contents are currently held by two institutions. The Hagley Library acquired part of the RCA Sarnoff Library several years ago, including some of the documents and audio data tapes discussed here. A number of prototype COSMAC systems and other artifacts, are part of The Sarnoff Collection at TCNJ. Some of those I've documented on my Web site, check my references below.

2017-18 activities on COSMAC coin-op arcade and related

In late 2017, some old RCA Sarnoff Library's "FRED" or COSMAC cassette tapes, were digitized by the Hagley Library. The digitization was a result of inquiries, as discussed in 2017 in the forum of classic gaming, about a "coin-op" COSMAC machine or prototype.. One challege about following "discussion group" dialogs, is the use of pseudonyms - it's hard to track actual names of persons, and so contact them directly.

The "techs" were looking for tapes for and information about the coin-op system. A number of persons contacted and visted The Hagley, obtained some documents, and identified some candidate tapes. The Hagley digitized a number of sample tapes, or as paid for by individuals, to confirm their methods of digitizing and to obtain likely coin-op candidate "game" programs. Some WAV files have been shared via that discussion forum. My (Herb Johnson's) involvement began, when Kevin Bunch from that forum asked ME about COSMAC data cassette formats, based on Web pages I have on the subject. LAter I was approached by Andy Modla, one of the atariage forum correspondants.

Kevin Bunch and more on the Hagley's tape archives

..."an amateur game historian down in Maryland", called the atariage discussion to my attention. As he introduced himself to me: "Hi Herb, my name's Kevin Bunch, I'm something of an amateur game historian down in Maryland. I recently learned about the Hagley library's Sarnoff collection, and how it includes a couple dozen data cassettes containing programs seemingly bound for the various 180x systems. Tapes include labels for the Studio II, the Studio III, the VIP, "Coin" (probably the arcade system), "Tag" (who knows), etc. The staff there graciously digitized one of the tapes for me as a test, labeled "Swords/Tag-Bowling" to see if it's possible to get usable data off it." - Kevin

Kevin further described events to me in May 2018: "From my recollection, I approached Hagley Museum & Library about visiting in early September 2017, which in turn led to me asking if they would like to try to digitize their tapes to see if it was possible to pull data off them. I requested Tag-Bowling/Swords as the "pilot" tape, since I knew Swords was planned to be an arcade game. Hagley's staff members, notably Kevin Martin and Lynsey Sczechowicz, were interested, as they didn't have any way of trying to get the [binary] data off of them and were hopeful that folks could come along at some point and assist with that."

"After some initial investigations of the audio file and the ideal format and settings for successful conversions, in October 2017 I requested some additional tapes be digitized from Hagley - other known arcade games and some that might have been Studio II files that might have been useful for comparing against known released software. In January 2018, Andy announced getting some of the first audio files I posted: Tag-Bowling, Swords, and Coin Bowling - working [as binary programs after] using his conversion tools, which he later posted publicly. This led to me requesting an additional tranche of tapes to be digitized in February, followed by my successful conversion of the arcade game Chase and what appears to be a WIP build of the arcade/FRED game Mines." - Kevin

Note from Herb: Much of what Kevin describes, was discussed by him and the people he references, in the forum I referenced above. In Sept 2018, Kevin released a YouTube video on the development history of the COSMAC. Title is Archive Annex Episode 1: RCA, FRED, and the Studio II and is part of "Atari Archive" on You Tube. Atari the company and game-platform, is not related to RCA's COSMAC or its games. It just happened that an Atari-focused email discussion group, was the on-line place where a number of COSMAC and games enthusiasts gathered, to discuss their work on early RCA COSMAC computer archives and artifacts. - Herb Johnson

Andy Modla

Andy Modla worked at RCA in the 1970's era on COSMAC products; he produced a number of programs. He's also part of that atariage online discussion, and he visited the Hagley and the Sarnoff Collection. In late 2017 he reviewed some of the Hagley's COSMAC content - documents and audio cassette tapes of COSMAC programs. Other people also visited the Hagley and obtained information. The material obtained, cover the coin-op prototype, and other COSMAC video-game prototypes - Studio III and Studio IV. Andy obtained several WAV files of digitized COSMAC tapes he and others identified as "coin op" or related to the Studio series. He used that content and tape data, to refine a COSMAC emulator to run coin-op games.

Here's Andy's github page of his COSMAC emulator and some of his results. The emulator is derived from Paul Robson's Studio II COSMAC emulator, as noted on his Web page. Andy offers a video of the emulation of the game he decoded from the coin-op tape WAV file. His github page provides the software source for his emulator and his software WAV to binary decoder for the coin-op audio tape.

Please note: several COSMAC systems were developed in the early 1970's, with several methods for producing audio tones to encode binary data. So, a "decoder" or one COSMAC emulator may not "decode" some other COSMAC's WAV files. I'll reference below, some notes I have about various COSMAC cassette-tape formats.

Paul Robson

As referenced by Andy Modla above, Paul Robson developed a Studio II software emulator in 2016. There's also an Arduino app and hardware, to produce Studio 2 like video signals on a NTSC video monitor. He has a number of studio II binaries available on his GitHub Web site. In 2016-17, as Paul obtained information on the "FRED" systems from the Hagley Library, he produced a FRED emulator and support for its CHIP-8 predecessor language "FEL", as documented by its RCA developers (Joe Weisbecker et al). His GitHub site shows a range of work upon 8-bit microprocessor vintage systems with various programming language implementations. Some of his COSMAC work can be found, on the Yahoo groups cosmacelf discussion group files area.

Herb Johnson

I live near and work with the Sarnoff Collection at TCNJ; which has several data-tapes, documents, and artifacts from Weisbecker's estate and from the former Sarnoff Library. One bit of work I did with the Sarnoff Collection is on another RCA COSMAC computer we call "a FRED 2". This is COSMAC hardware similar to the "coin-op" hardware. The Collections' Web site includes this FRED 2 as part of a 2018 exhibit on games and computing artifacts of Joseph Weisbecker. That system is similar in some ways to the coin-op COSMAC computer. The Collection also has the earliest of COSMAC prototypes, Joe Weisbecker's "System 00" which has a CMOS-chip prototype of what became the COSMAC microprocessor. Here's my Web page documentating the System 00, also referencing earlier reportage by Zbigniew Stachniak.

In Jan 2018, I'm working with the Sarnoff Collection curator Florencia Pierri, to digitize the Collection's COSMAC tapes, as encouraged by Andy Modla. Some of these tapes may be related to the coin-op arcade machine. Other tapes are of earlier or later COSMAC development tools or products. As the tapes are cataloged and digitized, their origins will hopefully become apparent. Since the Hagley's digitization produced WAV files which were "decodable", the Collection will try to follow that format - 96K samples/second, 24 bits/sample; and attempt to confirm the first WAV files produced can be "decoded" by the methods and programs and programmers discussed on this Web page.

COSMAC systems or prototypes used a variety of methods to represent binary data on audio cassettes. This linked Web page discusses the general technology of audio-cassette data on vintage computers. It points to other pages with specific COSMAC system audio tape methods.

Ed Keefe

Ed Keefe has worked for some time, on reproducing early COSMAC systems, as shown on his Web site. I contacted him late in 2017 to discuss WAV file formats and the Hagley's digitization results. He was very helpful and informative, as I discuss on my Web page about FRED data cassettes. I'll update this Web page section if Ed provides me with more information on the coin-op or other COSMAC tapes.

COSMAC emulators, ELF systems

There's a number of COSMAC software emulators of COSMAC hardware. These "encode" specific features of a number of COSMAC microcomputers, and even some of the prototype development systems. Some also are able to "read" WAV files made from COSMAC audio cassette data tapes, and "decode" them back to binary data - just as the original hardware would "listen" to the audio tapes and decode their binary content. I'll include this subject on this Web page, because these provide ways to decode WAV files and disassemble binaries. (Or I may move this to another Web page and put a link here instead.)

Andy Modla's emulator is described above, is derived from other COSMAC emulators. Follow the links on his WEb page to review those tools on their supporting Web sites. Often those sites include information about the emulated COSMAC computers, including ROM images and sample programs.

Marcel van Tongeren has supported for years, his Emma 02 COSMAC emulator. It supports many COSMACS including RCA's series of development systems, and COSMAC computers made by several companies. He's been very helpful to me, on emulating a COSMAC development computer I documented. As of about April 2018, Emma 02 supports the RCA "Coin Arcade" and recovered games. By summer 2018, it supports most if not all the binaries and COSMACS recovered. See Web pages linked at the top of this Web page for more of his COSMAC contributions; and notes at the end of the page for most-current results.

Michael Riley is another 21st century developer of COSMAC emulators, hardware and 1802 supporting languages. Not only does he emulate various ELF-like COSMACS, he supports a table-driven assembler for the 1802 and many other 8-bit microcomputers, and for CHIP-8. Also, he has a ELF/OS operating system, BASIC, FORTH and a LISP interpreter! These run on his hardware designs of various COSMAC computers with color graphics, sound and an IDE (PATA) drive.

There's a number of COSMAC "ELF" computer developers through the decades, since the original "ELF" article by Joe Weisbecker in the 1976 Popular Electronics magazine. A good Web site on the history of ELFs is operated by Dave Ruske and called There's links and documents there with more information and resources.

2018 work

The Sarnoff Collection's COSMAC tapes

The Sarnoff Collection's work on their RCA COSMAC cassettes tapes is discussed on the linked Web page. They are working in cooperation with the Hagley Library. By Summer 2018, the over-100 cassette tapes were digitized by curator Florencia Pierri, and archived on a shared file-system. Several people including myself, reviewed the files. They were digitized by Marcel van Tongreren over the next months of 2018 as described below.

the Hagley Library's COSMAC tapes

Kevin Bunch continued his update to me on May 3 2018, about ongoing work with the Hagley's COSMAC tapes. "Since Feb 2018, I've requested help from Ed Keefe and Marcel von Tongeren in converting the VIP-formatted files, as I've had trouble using Andy's conversion program (I'm not a programmer and didn't want to constantly ask Andy to troubleshoot every issue I had with it). Ed emailed me some VIP programs he successfully tested on his hardware and proceeded to convert to binaries in April, and Marcel has been keeping me informed of his work converting tapes from Hagley into Studio and VIP/ELF formats the past few days using the Emma 02 emulator as a conversion tool. between the two of them, about half of the VIP tapes I've had digitized have so far been successfully converted, along with a number of programs for the Studio II and III (including some color demos for the Studio III). As that array of tapes is getting converted, I plan on requesting the remaining Hagley tapes be digitized in the coming weeks. As tapes get converted [to binaries], I've been sending the files to the Hagley Museum staff for their own archiving and plans." - Kevin

As Kevin notes, Marcel's EMMA 02 includes Studio II, II, and IV emulation. There's also Studio II and IV games, screens and support information on Andy Modla's rca-studio2 github site. as of May 2018.

In May 22 2018, Kevin said, "Marcel has gotten nearly all of the digitized Hagley tapes converted to binary, save for about four programs or so that are still proving stubborn. These include a number of VIP and Elf programs, demos and games, a tape containing the Chip8 programming language, a seemingly complete build of the Mines arcade game, some other builds of Computer Bowling. [There's] a few Studio II [and] VIP versions of released games (and a prototype build of its built in games, including a few not included in the final console), some Studio III demos. [And there's] a couple that seem to just not work due to corruption. Hagley has given him the go-ahead to include whatever files he wants with the next build of Emma 02 [COSMAC emulator] as long as they're attributed to the [Hagley Museum]."

"I've put in a formal request to Hagley Museum to digitize the remaining 11 or so tapes in their collection; based on the labels these seem to mostly be computer languages and development utilities, with maybe a couple VIP games mixed in. Those should be done within the next week or so." - Kevin

COSMAC tapes processed, programs recovered

By the end of summer 2018, all the Hagley's COSMAC tapes were digitized, and in the hands of various developers who "recovered" their binary contents. The same applies to the Sarnoff Collection's COSMAC tapes. By fall 2018, Marcel's EMMA 02 emulator included those binaries from both sites, and simulates the COSMAC computers they were developed upon and run. Other emulators, as reported on this Web page, also support some of those binaries and emulate some of those COSMAC systems.

Sometime in Nov 2018, the Hagley Library published on their Web site, what they call the Joe Weisbecker Video Game Collection. It's WAV files from their digitized audio cassette tapes, then converted to binaries by various programs (discussed on this Web page), and run under Marcel van Tongreren's EMMA 02 emulator. (They were also run with other emulators, as previously discussed). The Web site shows a mix of WAV files, music recordings, "extracted binaries" (programs), and a few manuals and game-play videos among the 130 files.

Public-accessable archives of the Sarnoff Collection's binaries and WAV files are under discussion, as of Dec 2018. There's over 100 tapes digitized, and dozens of programs extracted, identified by computer, and verified.

However, binaries from both the Sarnoff Collection and the Hagley are incorporated into recent (late 2018) versions of the EMMA 02 COSMAC emulator. The program binaries are organized by COSMAC computer and program name; some reference audio files where a voice or sound was part of the game-play.


It's amazing work done, considering all the steps taken. Audio cassette tapes, recorded in the mid-1970's - some over forty years old - were read on ordinary audio equipment and a USB digitizer. They wer digitized into huge WAV files, then interpreted by software not hardware into their original binaries. Based on fragments of development documents and a few preserved pieces of hardware, original COSMAC prototype computers were re-engineered into software emulators. Those emulators represented not only well-known 1802 and "1801" CMOS microprocessors, but previously-unknown CMOS logic-level hardware prototypes with no microprocessors whatsoever! The binary programs were not only "recovered", but disassembled back to COSMAC assembly language for further analysis, to refine the emulators and to verify emulated instruction sets and hardware. Even the audio effects on the cassette tapes were properly emulated - all decades later.

In the course of Marcel's work, he's found and described a number of CHIP-8 like "languages" for the various COSMAC prototypes, and confirmed variations known and in use in the VIP, Studio II, "System 00", "FRED"s. Again - the various Web sites for these COSMAC emulators, describe and report on some of these.

- Herb Johnson

Contact information:
Herb Johnson
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This page and edited content is copyright Herb Johnson (c) 2018. Copyright of other contents beyond brief quotes, is held by those authors. Contact Herb at, an email address is available on that page..