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Cosmac VIP




Home Computer






CHIP-8 interpreter


Hexadecimal membrane keyboard, 16 keys


RCA CDP-1802


1.7609 MHz (4.54 microsecond per machine cycle)


RCA CDP-1861 video chip


1 kb (VP-111) or 2 Kb (VIP), upgradeable to 32 kb


VP-111 : 1 kb
VIP : 4 kb CMOS ROM + 512 byte Monitor ROM


Texts are displayed using graphical features


64 x 32


Black & white


1.4 kHz tone generator. Output may be connected to any small standard 8 ohm speaker


8.5'' x 11'' x 1'' / 2.2 lbs


Video output, tape cassette interface (100 bytes per second)


VP-111 : +5.0 +/- 0.25 VDC @ 250 mA
VIP : 5v dc, 600mA


Expansion interface, Parallel I/O interface


$275 (USA, 1977)


Cosmac VIP

The Cosmac VIP, originally 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 in August 76 and teh 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 equipped 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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