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R > RCA > Cosmac VIP   

Cosmac VIP

The Cosmac VIP, originaly named VP-111, is a typical hobbyist "single-board" computer sold as a kit. You had to build it yourself ! The system uses a RCA CDP-1802 microprocessor like the RCA Studio II video game system. In fact the Studio II is very similar to the VIP and can be considered as its video-game version. But the VIP is also somehow an improved version of the original Cosmac Elf board system, described in Popular Electronics magazine, august 76 and the following months. The CDP-1802 CPU was also used as the heart of the Voyager, Viking and Galileo probes ! Until recently the 1802 was quite popular (for alarm systems for example) thanks to its CMOS technology ideal for low power systems.

The Cosmac VIP has a most basic hexadecimal keyboard (16 keys). The language stored in ROM is called CHIP-8 and is only 512 bytes long ! It consists of 31 instructions each of which is two bytes (or four hex digits) long. It's a kind of simplified machine language. 16 one-byte variables are provided. Subroutine nesting and machine language inserts are permitted. CHIP-8 was quite popular at that time (Telmac 1800, ETI 660 and DREAM 6800 used it) as it allowed to program video games easily. CHIP-8 was not only used in the late 70's and early 80's. It was used in the early 90's on the HP48 calculator because there was no programming tools to develop fast games on it. Then, a better version of CHIP-8 appeared: SUPER-CHIP. This interpreter has all the CHIP-8 features, as well as and some new ones like a 128*64 resolution (source : David Winter).
RCA also sold Tiny Basic, a simple Basic interpreter, as a 4K ROM on an expansion board.

With this system, basic functions are : type programs into RAM from the hex keyboard, save and load programs on tapes, display memory bytes in hex on CRT, step through RAM contents and examine microprocessor registers. Wow.

The Cosmac VIP is equiped with a sound chip and a real-time crystal clock. The sound produced can be heard through the tape output connector. It was delivered with some documentations (CHIP-8, machine language) and listings of 20 video games !

To the left of the hexadecimal keyboard are a reset switch and LED indicators for power-on and cassette operation. Memory add-ons, expansion port and parallel interface are pre-wired on the motherboard but have to be implemented as options. With the I/O interface, you could connect interface relays, sensors, printers or ASCII keyboards.

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The Cosmac VIP was our first computer and my brother and I spent many hours programming it and having fun. Living in Australia, my Dad had it shipped from the US (via my Uncle) and we assembled one weekend.

My brother learned the assembly language and he hacked the video subroutines and created some pretty interesting effects. I am sure it was not too good for the monitor, but one effect was to get the top of the display to fold back in itself (at least that is what it looked like). The he made a terrain type routine that looked like the ground curving onto the screen from the top and disappearing off the bottom.

We added RAM to the board, we had one of our friends burn the CHIP8 language into a ROM and also had the ROM dual boot into two different load states (I think one had the CHIP8 loaded and the other didn’t). We got hold of the ASCII keyboard but never really did anything with it, it was a pretty cool keyboard and used a membrane rather than keys. Very hard to use as there was no tactile feedback at all.

I used to take the Cosmac and a monitor to school and we would play it during recess. One of the games I wrote was a car racing game and to work around my limited knowledge of sprite collision detection I would draw one frame with the cars on it and test for collision, then draw another frame with the cars and scenery which did not detect for collision. As you can imagine, the scenery frame flickered quite a bit, but overall the game went pretty well and all my friends were pretty impressed.

Monday 4th August 2008
Jason Panosh (Alfredton, Australia)

One of the CPU''s I''m very fond of is the CDP1802 by RCA. I had bought this RCA Integrated Circuits data book (I *loved* to read this kind of books) and there was that IC that at first I didn''t understand what it was doing (most of the others were from the TTL 74xx series), until it dawned on me that this was an entire computer in a single IC. One of the landmark events of my life...

Sunday 14th February 2021
Mario (Switzerland)

I too imported a Cosmac kit from the US (to NZ at that time) in the early 70s, and built it. Great fun programming this thing in hex code !

Tuesday 17th July 2012
Shane Doyle (Australia)


NAME  Cosmac VIP
TYPE  Home Computer
YEAR  1977
KEYBOARD  Hexadecimal membrane keyboard, 16 keys
SPEED  1.7609 MHz (4.54 microsecond per machine cycle)
CO-PROCESSOR  RCA CDP-1861 video chip
RAM  1 kb (VP-111) or 2 Kb (VIP), upgradable to 32 kb
ROM  VP-111 : 1 kb
VIP : 4 kb CMOS ROM + 512 byte Monitor ROM
TEXT MODES  Texts are displayed using graphical features
COLORS  Black & white
SOUND  1.4 kHz tone generator. Ouput may be connected to any small standard 8 ohm speaker
SIZE / WEIGHT  8.5'' x 11'' x 1'' / 2.2 lbs
I/O PORTS  Video output, tape cassette interface (100 bytes per second)
POWER SUPPLY  VP-111 : +5.0 +/- 0.25 VDC @ 250 mA
VIP : 5v dc, 600mA
PERIPHERALS  Expansion interface, Parallel I/O interface
PRICE  $275 (USA, 1977)

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