April 21st, 2011 ~ by admin

Inside the 1802: a Visual6502.org View


RCA 1802E Die - 20x magnification - Visual6502.org

The talent at Visual6502.org continues.  After imaging and building a complete simulator for the MOS 6502 they did the same for the Motorola 6800 (from which the 6502 was based).

We have sent Visual6502.org several chips and they have now imaged the RCA 1802 that we sent.  What is very interesting is how little marking are on the die, the only that I could see was the number ’10824.’  This particular chip was dated early 1981 though the 1802 COSMAC was designed in 1976 and was one of the first CMOS microprocessors.  The 1802 had around 5000 transistors (Visual6502 will let us know exactly how many once they are done, and of course what each and every one of them does). For higher res shots and more info see here

September 4th, 2010 ~ by admin

From Video Games to Deep Space – The RCA 1802 COSMAC

iFixit has been doing a series of ‘retro’ teardowns. Looking at various early video game consoles. SO far they have done the following:

All of these systems are pretty interesting designs, however we are going to take a peek at the RCA Studio II.  This was RCAs try at the video game console market that was emerging in the 1970s.  It sadly was outclassed soon after its introduction by the likes of the Atari 2600 and was discontinued after a mere 2 years.  At the heart of the Studio II was a CPU that RCA developed in 1976, a CPU that has outlived the Studio II, and many many other consoles, in fact the RCA COSMAC 1802 (the single chip implementation of the 2 chip 1801) is still made today by Intersil.

RCA Studio II 1802 Processor - 1976

The 1802 in the console iFixit used is a very uncommon white ceramic package, and is dated 7645, the 1802 was introduced in the first half of 1976 so this is a very early example.  The 1802 was one of the first static CMOS designs.  It didn’t have a minimum clock frequency so could be sped up/down according to the needs of the design (and power constraints). In the Studio II it ran at 1.7MHz. Other versions ran at 3.2MHz-6.4MHz.  One interesting note with the design of the COSMAC was that its frequency responded nearly linearly with supply voltage.  At the standard supply of 5V the frequency was 3.2MHz, However, double the supply voltage to 10V and the 1802 would be able to run at 6.4MHz (this only on certain specs of the chip obviously)

Harris CDP1802ACD3 -1992

Today the 1802, due to its flexible 16×16 register design, and well known reliability in harsh environments lives on in dozens of satellites circling the Earth.  It was also used as the main computer (6 1802s actually) in the Galileo deep space mission to Jupiter.  Many of the CPU’s designed in the 1970s (and often used in video games of the time) still are made (by Intersil now) and used today.   THe 1802, 6502, PIC16, and 2901 to name a few.  So next time you enjoy the weather report, or watch some satellite TV, its likely that a CPU designed over 35 years ago is being used to get that content to you.

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